wstools-py3/XMLSchema.py

# Copyright (c) 2003, The Regents of the University of California,
# through Lawrence Berkeley National Laboratory (subject to receipt of
# any required approvals from the U.S. Dept. of Energy).  All rights
# reserved. 
#
# Copyright (c) 2001 Zope Corporation and Contributors. All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.0 (ZPL).  A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.

ident = "$Id$"

import types, weakref, urllib, sys
from threading import RLock
from xml.dom.ext import SplitQName
from xml.ns import SCHEMA, XMLNS, SOAP, WSDL
from Utility import DOM, Collection
from StringIO import StringIO

def GetSchema(component):
    """convience function for finding the parent XMLSchema instance.
    """
    parent = component
    while not isinstance(parent, XMLSchema):
        parent = parent._parent()
    return parent
    
class SchemaReader:
    """A SchemaReader creates XMLSchema objects from urls and xml data.
    """
    def __init__(self, domReader=None):
        """domReader -- class must implement DOMAdapterInterface
        """
        self.__readerClass = domReader
        if not self.__readerClass:
            self.__readerClass = DOMAdapter
        self._includes = {}
        self._imports = {}

    def __setImports(self, schema):
        """Add dictionary of imports to schema instance.
           schema -- XMLSchema instance
        """
        for ns,val in schema.imports.items(): 
            if self._imports.has_key(ns):
                schema.addImportSchema(self._imports[ns])

    def __setIncludes(self, schema):
        """Add dictionary of includes to schema instance.
           schema -- XMLSchema instance
        """
        for schemaLocation, val in schema.includes.items(): 
            if self._includes.has_key(schemaLocation):
                schema.addIncludeSchema(self._imports[schemaLocation])

    def addSchemaByLocation(self, location, schema):
        """provide reader with schema document for a location.
        """
        self._includes[location] = schema

    def addSchemaByNamespace(self, schema):
        """provide reader with schema document for a targetNamespace.
        """
        self._imports[schema.targetNamespace] = schema

    def loadFromNode(self, parent, element):
        """element -- DOM node or document
           parent -- WSDLAdapter instance
        """
        reader = self.__readerClass(element)
        schema = XMLSchema(parent)
        #HACK to keep a reference
        schema.wsdl = parent
        schema.load(reader)
        return schema
        
    def loadFromStream(self, file):
        """Return an XMLSchema instance loaded from a file object.
           file -- file object
        """
        reader = self.__readerClass()
        reader.loadDocument(file)
        schema = XMLSchema()
        schema.load(reader)
        self.__setIncludes(schema)
        self.__setImports(schema)
        return schema

    def loadFromString(self, data):
        """Return an XMLSchema instance loaded from an XML string.
           data -- XML string
        """
        return self.loadFromStream(StringIO(data))

    def loadFromURL(self, url):
        """Return an XMLSchema instance loaded from the given url.
           url -- URL to dereference
        """
        if not url.endswith('xsd'):
            raise SchemaError, 'unknown file type %s' %url
        reader = self.__readerClass()
        reader.loadFromURL(url)
        schema = XMLSchema()
        schema.load(reader)
        self.__setIncludes(schema)
        self.__setImports(schema)

    def loadFromFile(self, filename):
        """Return an XMLSchema instance loaded from the given file.
           filename -- name of file to open
        """
        file = open(filename, 'rb')
        try:     schema = self.loadFromStream(file)
        finally: file.close()
        return schema


class SchemaError(Exception): 
    pass

###########################
# DOM Utility Adapters 
##########################
class DOMAdapterInterface:
    def hasattr(self, attr):
        """return true if node has attribute 
           attr - attribute to check for
        """
        raise NotImplementedError, 'adapter method not implemented'

    def getContentList(self, *contents):
        """returns an ordered list of child nodes
           *contents -- list of node names to return
        """
        raise NotImplementedError, 'adapter method not implemented'

    def setAttributeDictionary(self, attributes):
        """set attribute dictionary
        """
        raise NotImplementedError, 'adapter method not implemented'

    def getAttributeDictionary(self):
        """returns a dict of node's attributes
        """
        raise NotImplementedError, 'adapter method not implemented'

    def getTagName(self):
        """returns tagName of node
        """
        raise NotImplementedError, 'adapter method not implemented'

    def loadDocument(self, file):
        """load a Document from a file object
           file --
        """
        raise NotImplementedError, 'adapter method not implemented'

    def loadFromURL(self, url):
        """load a Document from an url
           url -- URL to dereference
        """
        raise NotImplementedError, 'adapter method not implemented'


class DOMAdapter(DOMAdapterInterface):
    """Adapter for ZSI.Utility.DOM
    """
    def __init__(self, node=None):
        """Reset all instance variables.
           element -- DOM document, node, or None
        """
        if hasattr(node, 'documentElement'):
            self.__node = node.documentElement
        else:
            self.__node = node
        self.__attributes = None

    def hasattr(self, attr):
        """XXX assuming all xsd attributes not prefixed,
           all others are.  Should ask xmlInterface so
           it can take care namespace mapping for
           prefixed attributes
        """
        if not self.__attributes:
            self.setAttributeDictionary()
        return self.__attributes.has_key(attr)

    def getContentList(self, *contents):
        nodes = []
        ELEMENT_NODE = self.__node.ELEMENT_NODE
        for child in DOM.getElements(self.__node, None):
            if child.nodeType == ELEMENT_NODE and\
               SplitQName(child.tagName)[1] in contents:
                nodes.append(child)
        return map(self.__class__, nodes)

    def setAttributeDictionary(self):
        self.__attributes = {}
        for v in self.__node._attrs.values():
            self.__attributes[v.nodeName] = v.nodeValue

    def getAttributeDictionary(self):
        if not self.__attributes:
            self.setAttributeDictionary()
        return self.__attributes

    def getTagName(self):
        return self.__node.tagName

    def loadDocument(self, file):
        self.__node = DOM.loadDocument(file)
        if hasattr(self.__node, 'documentElement'):
            self.__node = self.__node.documentElement

    def loadFromURL(self, url):
        self.__node = DOM.loadFromURL(url)
        if hasattr(self.__node, 'documentElement'):
            self.__node = self.__node.documentElement

 
class XMLBase: 
    """ These class variables are for string indentation.
    """ 
    __indent = 0
    __rlock = RLock()

    def __str__(self):
        XMLBase.__rlock.acquire()
        XMLBase.__indent += 1
        tmp = "<" + str(self.__class__) + '>\n'
        for k,v in self.__dict__.items():
            tmp += "%s* %s = %s\n" %(XMLBase.__indent*'  ', k, v)
        XMLBase.__indent -= 1 
        XMLBase.__rlock.release()
        return tmp

##########################################################
# Schema Components
#########################################################
class XMLSchemaComponent(XMLBase):
    """
       class variables: 
           required -- list of required attributes
           attributes -- dict of default attribute values, including None.
               Value can be a function for runtime dependencies.
           contents -- dict of namespace keyed content lists.
               'xsd' content of xsd namespace.
    """
    required = []
    attributes = {}
    contents = {}
    xmlns_key = ''
    xmlns = 'xmlns'
    xml = 'xml'
    xsd = 'xsd'
    wsdl = 'wsdl'
    soap = 'soap'
    soapenc = 'soapenc'
    mime = 'mime'
    http = 'http'

    def __init__(self, parent=None):
        """parent -- parent instance
           instance variables:
               attributes -- dictionary of node's attributes
        """
        self.attributes = None
        self._parent = parent
        if self._parent:
            self._parent = weakref.ref(parent)

        if not self.__class__ == XMLSchemaComponent\
           and not (type(self.__class__.required) == type(XMLSchemaComponent.required)\
           and type(self.__class__.attributes) == type(XMLSchemaComponent.attributes)\
           and type(self.__class__.contents) == type(XMLSchemaComponent.contents)):
            raise RuntimeError, 'Bad type for a class variable in %s' %self.__class__

    def getTargetNamespace(self):
        """return targetNamespace
        """
        parent = self
        targetNamespace = 'targetNamespace'
        tns = self.attributes[XMLSchemaComponent.xsd].get(targetNamespace)
        while not tns:
            parent = parent._parent()
            print parent
            print parent.attributes[XMLSchemaComponent.xsd]
            tns = parent.attributes[XMLSchemaComponent.xsd].get(targetNamespace)
        return tns

    def getTypeDefinition(self, attribute):
        """attribute -- attribute with a QName value (eg. type).
           collection -- check types collection in parent Schema instance
        """
        return self.getQNameAttribute('types', attribute)

    def getElementDeclaration(self, attribute):
        """attribute -- attribute with a QName value (eg. element).
           collection -- check elements collection in parent Schema instance.
        """
        return self.getQNameAttribute('elements', attribute)

    def getQNameAttribute(self, collection, attribute):
        """returns object instance representing QName --> (namespace,name),
           or if does not exist return None.
           attribute -- an information item attribute, with a QName value.
           collection -- collection in parent Schema instance to search.
        """
        obj = None
        tdc = self.attributes[XMLSchemaComponent.xsd].get(attribute)
        if tdc:
            parent = GetSchema(self)
            if parent.targetNamespace == tdc.getTargetNamespace():
                obj = getattr(parent, collection)[tdc.getName()]
            elif parent.imports.has_key(tdc.getTargetNamespace()):
                schema = parent.imports[tdc.getTargetNamespace()].getSchema()
                obj = getattr(schema, collection)[tdc.getName()]
        return obj

    def getXMLNS(self, prefix=None):
        """retrieve contents
           empty string returns 'xmlns'
        """
        parent = self
        ns = self.attributes[XMLSchemaComponent.xmlns].get(prefix)
        while not ns:
            parent = parent._parent()
            ns = parent.attributes[XMLSchemaComponent.xmlns].get(prefix or XMLSchemaComponent.xmlns_key)
        return ns

    def getAttribute(self, attribute):
        """return requested attribute or None
        """
        return self.attributes[XMLSchemaComponent.xsd].get(attribute)
 
    def setAttributes(self, node):
        """Sets up attribute dictionary, checks for required attributes and 
           sets default attribute values. attr is for default attribute values 
           determined at runtime.

           attribute dictionary is prefix keyed by 
             xml
             xmlns
             xsd
             wsdl
             soap
 
           all other keys are namespace values.
        """
        self.attributes = {XMLSchemaComponent.xsd:{},\
                           XMLSchemaComponent.xmlns:{}}
        for k,v in node.getAttributeDictionary().items():
            prefix,value = SplitQName(k)
            if value == XMLSchemaComponent.xmlns:
                self.attributes[value][prefix or XMLSchemaComponent.xmlns_key] = v
            elif prefix:
                ns = node.getNamespace(prefix)
                if ns == XMLNS or prefix == XMLSchemaComponent.xml:
                    if not self.attributes.has_key(XMLSchemaComponent.xml):
                        self.attributes[XMLSchemaComponent.xml] = {}
                    self.attributes[XMLSchemaComponent.xml][k] = v
                elif ns in SCHEMA.XSD_LIST:
                    self.attributes[XMLSchemaComponent.xsd][value] = v
                elif ns == WSDL.BASE:
                    if not self.attributes.has_key(XMLSchemaComponent.wsdl):
                        self.attributes[XMLSchemaComponent.wsdl] = {}
                    self.attributes[XMLSchemaComponent.wsdl][value] = v
                elif ns == WSDL.BIND_HTTP:
                    if not self.attributes.has_key(XMLSchemaComponent.http):
                        self.attributes[XMLSchemaComponent.http] = {}
                    self.attributes[XMLSchemaComponent.http][value] = v
                elif ns == WSDL.BIND_MIME:
                    if not self.attributes.has_key(XMLSchemaComponent.mime):
                        self.attributes[XMLSchemaComponent.mime] = {}
                    self.attributes[XMLSchemaComponent.mime][value] = v
                elif ns == WSDL.BIND_SOAP:
                    if not self.attributes.has_key(XMLSchemaComponent.soap):
                        self.attributes[XMLSchemaComponent.soap] = {}
                    self.attributes[XMLSchemaComponent.soap][value] = v
                else:
                    self.attributes[ns][value] = v
            else:
                #UNPREFIXED Attribute
                self.attributes[XMLSchemaComponent.xsd][value] = v

        self.__checkAttributes()
        self.__setAttributeDefaults()

        #set QNames
        for k in ['type', 'element', 'base', 'ref', 'substitutionGroup', 'itemType']:
            if self.attributes[XMLSchemaComponent.xsd].has_key(k):
                prefix, value = SplitQName(self.attributes[XMLSchemaComponent.xsd].get(k))
                self.attributes[XMLSchemaComponent.xsd][k] = \
                    TypeDescriptionComponent((self.getXMLNS(prefix), value))

        #Union, memberTypes is a whitespace separated list of QNames
        if self.attributes[XMLSchemaComponent.xsd].has_key('memberTypes'):
            qnames = self.attributes[XMLSchemaComponent.xsd]['memberTypes']
            

    def getContents(self, node):
        """retrieve xsd contents
        """
        return node.getContentList(*self.__class__.contents[XMLSchemaComponent.xsd])

    def __setAttributeDefaults(self):
        """Looks for default values for unset attributes.  If
           class variable representing attribute is None, then
           it must be defined as an instance variable.
        """
        for k,v in self.__class__.attributes.items():
            if v and not self.attributes[XMLSchemaComponent.xsd].has_key(k):
                if isinstance(v, types.FunctionType):
                    self.attributes[XMLSchemaComponent.xsd][k] = v(self)
                else:
                    self.attributes[XMLSchemaComponent.xsd][k] = v

    def __checkAttributes(self):
        """Checks that required attributes have been defined,
           attributes w/default cannot be required.   Checks
           all defined attributes are legal.
        """
        for a in self.__class__.required:
            if not self.attributes[XMLSchemaComponent.xsd].has_key(a):
                raise SchemaError,\
                    'class instance %s, missing required attribute %s'\
                    %(self.__class__, a)

        for a in self.attributes[XMLSchemaComponent.xsd].keys():
            if a not in self.__class__.attributes.keys():
                raise SchemaError, '%s, unknown attribute' %a


class WSDLToolsAdapter(XMLSchemaComponent):
    """WSDL Adapter to grab the attributes from the wsdl document node.
    """
    attributes = {'name':None, 'targetNamespace':None}

    def __init__(self, wsdl):
        XMLSchemaComponent.__init__(self, None)
        self.setAttributes(DOMAdapter(wsdl.document))

    def getImportSchemas(self):
        """returns WSDLTools.WSDL types Collection
        """
        return self._parent().types

"""Marker Interface:  can determine something about an instances properties by using 
        the provided convenience functions.

"""
class DefinitionMarker: 
    """marker for definitions
    """
    pass

class DeclarationMarker: 
    """marker for declarations
    """
    pass

class AttributeMarker: 
    """marker for attributes
    """
    pass

class AttributeGroupMarker: 
    """marker for attribute groups
    """
    pass

class WildCardMarker: 
    """marker for wildcards
    """
    pass

class ElementMarker: 
    """marker for wildcards
    """
    pass

class ReferenceMarker: 
    """marker for references
    """
    pass

class ModelGroupMarker: 
    """marker for model groups
    """
    pass

class ExtensionMarker: 
    """marker for extensions
    """
    pass

class RestrictionMarker: 
    """marker for restrictions
    """
    facets = ['enumeration', 'length', 'maxExclusive', 'maxInclusive',\
        'maxLength', 'minExclusive', 'minInclusive', 'minLength',\
        'pattern', 'fractionDigits', 'totalDigits', 'whiteSpace']

class SimpleMarker: 
    """marker for simple type information
    """
    pass

class ComplexMarker: 
    """marker for complex type information
    """
    pass

class MarkerInterface:
    def isDefinition(self):
        return isinstance(self, DefinitionMarker)

    def isDeclaration(self):
        return isinstance(self, DeclarationMarker)

    def isAttribute(self):
        return isinstance(self, AttributeMarker)

    def isAttributeGroup(self):
        return isinstance(self, AttributeGroupMarker)

    def isReference(self):
        return isinstance(self, ReferenceMarker)

    def isWildCard(self):
        return isinstance(self, WildCardMarker)

    def isModelGroup(self):
        return isinstance(self, ModelGroupMarker)

    def isExtension(self):
        return isinstance(self, ExtensionMarker)

    def isRestriction(self):
        return isinstance(self, RestrictionMarker)

    def isSimple(self):
        return isinstance(self, SimpleMarker)

    def isComplex(self):
        return isinstance(self, ComplexMarker)


class Notation(XMLSchemaComponent):
    """<notation>
       parent:
           schema
       attributes:
           id -- ID
           name -- NCName, Required
           public -- token, Required
           system -- anyURI
       contents:
           annotation?
    """
    required = ['name', 'public']
    attributes = {'id':None, 'name':None, 'public':None, 'system':None}
    contents = {'xsd':('annotation')}

    def __init__(self, parent):
        XMLSchemaComponent.__init__(self, parent)
        self.annotation = None

    def fromDom(self, node):
        self.setAttributes(node)
        contents = self.getContents(node)

        for i in contents:
            component = SplitQName(i.getTagName())[1]
            if component == 'annotation' and not self.annotation:
                self.annotation = Annotation(self)
                self.annotation.fromDom(i)
            else:
                raise SchemaError, 'Unknown component (%s)' %(i.getTagName())


class Annotation(XMLSchemaComponent):
    """<annotation>
       parent:
           all,any,anyAttribute,attribute,attributeGroup,choice,complexContent,
           complexType,element,extension,field,group,import,include,key,keyref,
           list,notation,redefine,restriction,schema,selector,simpleContent,
           simpleType,union,unique
       attributes:
           id -- ID
       contents:
           (documentation | appinfo)*
    """
    attributes = {'id':None}
    contents = {'xsd':('documentation', 'appinfo')}

    def __init__(self, parent):
        XMLSchemaComponent.__init__(self, parent)
        self.content = None

    def fromDom(self, node):
        self.setAttributes(node)
        contents = self.getContents(node)
        content = []

        for i in contents:
            component = SplitQName(i.getTagName())[1]
            if component == 'documentation':
                #print_debug('class %s, documentation skipped' %self.__class__, 5)
                continue
            elif component == 'appinfo':
                #print_debug('class %s, appinfo skipped' %self.__class__, 5)
                continue
            else:
                raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
        self.content = tuple(content)


    class Documentation(XMLSchemaComponent):
        """<documentation>
           parent:
               annotation
           attributes:
               source, anyURI
               xml:lang, language
           contents:
               mixed, any
        """
        attributes = {'source':None, 'xml:lang':None}
        contents = {'xsd':('mixed', 'any')}

        def __init__(self, parent):
            XMLSchemaComponent.__init__(self, parent)
            self.content = None

        def fromDom(self, node):
            self.setAttributes(node)
            contents = self.getContents(node)
            content = []

            for i in contents:
                component = SplitQName(i.getTagName())[1]
                if component == 'mixed':
                    #print_debug('class %s, mixed skipped' %self.__class__, 5)
                    continue
                elif component == 'any':
                    #print_debug('class %s, any skipped' %self.__class__, 5)
                    continue
                else:
                    raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
            self.content = tuple(content)


    class Appinfo(XMLSchemaComponent):
        """<appinfo>
           parent:
               annotation
           attributes:
               source, anyURI
           contents:
               mixed, any
        """
        attributes = {'source':None, 'anyURI':None}
        contents = {'xsd':('mixed', 'any')}

        def __init__(self, parent):
            XMLSchemaComponent.__init__(self, parent)
            self.content = None

        def fromDom(self, node):
            self.setAttributes(node)
            contents = self.getContents(node)
            content = []

            for i in contents:
                component = SplitQName(i.getTagName())[1]
                if component == 'mixed':
                    #print_debug('class %s, mixed skipped' %self.__class__, 5)
                    continue
                elif component == 'any':
                    #print_debug('class %s, any skipped' %self.__class__, 5)
                    continue
                else:
                    raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
            self.content = tuple(content)


class XMLSchemaFake:
    # This is temporary, for the benefit of WSDL until the real thing works.
    def __init__(self, element):
        self.targetNamespace = DOM.getAttr(element, 'targetNamespace')
        self.element = element

class XMLSchema(XMLSchemaComponent):
    """A schema is a collection of schema components derived from one
       or more schema documents, that is, one or more <schema> element
       information items. It represents the abstract notion of a schema
       rather than a single schema document (or other representation).

       <schema>
       parent:
           ROOT
       attributes:
           id -- ID
           version -- token
           xml:lang -- language
           targetNamespace -- anyURI
           attributeFormDefault -- 'qualified' | 'unqualified', 'unqualified'
           elementFormDefault -- 'qualified' | 'unqualified', 'unqualified'
           blockDefault -- '#all' | list of 
               ('substitution | 'extension' | 'restriction')
           finalDefault -- '#all' | list of 
               ('extension' | 'restriction' | 'list' | 'union')
        
       contents:
           ((include | import | redefine | annotation)*, 
            (attribute, attributeGroup, complexType, element, group, 
             notation, simpleType)*, annotation*)*


        attributes -- schema attributes
        imports -- import statements
        includes -- include statements
        redefines -- 
        types    -- global simpleType, complexType definitions
        elements -- global element declarations
        attr_decl -- global attribute declarations
        attr_groups -- attribute Groups
        model_groups -- model Groups
        notations -- global notations
    """
    attributes = {'id':None, 
        'version':None, 
        'xml:lang':None, 
        'targetNamespace':None,
        'attributeFormDefault':'unqualified',
        'elementFormDefault':'unqualified',
        'blockDefault':None,
        'finalDefault':None}
    contents = {'xsd':('include', 'import', 'redefine', 'annotation', 'attribute',\
                'attributeGroup', 'complexType', 'element', 'group',\
                'notation', 'simpleType', 'annotation')}
    empty_namespace = ''

    def __init__(self, parent=None): 
        """parent -- 
           instance variables:
           targetNamespace -- schema's declared targetNamespace, or empty string.
           _imported_schemas -- namespace keyed dict of schema dependencies, if 
              a schema is provided instance will not resolve import statement.
           _included_schemas -- schemaLocation keyed dict of component schemas, 
              if schema is provided instance will not resolve include statement.
           _base_url -- needed for relative URLs support, only works with URLs
               relative to initial document.
           includes -- collection of include statements
           imports -- collection of import statements
           elements -- collection of global element declarations
           types -- collection of global type definitions
           attr_decl -- collection of global attribute declarations
           attr_groups -- collection of global attribute group definitions
           model_groups -- collection of model group definitions
           notations -- collection of notations

        """
        self.targetNamespace = None
        XMLSchemaComponent.__init__(self, parent)
        f = lambda k: k.attributes['name']
        self.includes = Collection(self, key=f)
        self.imports = Collection(self, key=f)
        self.elements = Collection(self, key=f)
        self.types = Collection(self, key=f)
        self.attr_decl = Collection(self, key=f)
        self.attr_groups = Collection(self, key=f)
        self.model_groups = Collection(self, key=f)
        self.notations = Collection(self, key=f)

        self._imported_schemas = {}
        self._included_schemas = {}
        self._base_url = None

    def addImportSchema(self, schema):
        """for resolving import statements in Schema instance
           schema -- schema instance
           _imported_schemas 
        """
        if not isinstance(schema, Schema):
            raise TypeError, 'expecting a Schema instance'
        if schema.targetNamespace != self.targetNamespace:
            self._imported_schemas[schema.targetNamespace]
        else:
            raise SchemaError, 'import schema bad targetNamespace'

    def addIncludeSchema(self, schemaLocation, schema):
        """for resolving include statements in Schema instance
           schemaLocation -- schema location
           schema -- schema instance
           _included_schemas 
        """
        if not isinstance(schema, Schema):
            raise TypeError, 'expecting a Schema instance'
        if not schema.targetNamespace or\
             schema.targetNamespace == self.targetNamespace:
            self._included_schemas[schemaLocation] = schema
        else:
            raise SchemaError, 'include schema bad targetNamespace'
        
    def setImportSchemas(self, schema_dict):
        """set the import schema dictionary, which is used to 
           reference depedent schemas.
        """
        self._imported_schemas = schema_dict

    def getImportSchemas(self):
        """get the import schema dictionary, which is used to 
           reference depedent schemas.
        """
        return self._imported_schemas

    def getSchemaNamespacesToImport(self):
        """returns tuple of namespaces the schema instance has declared
           itself to be depedent upon.
        """
        return tuple(self.includes.keys())

    def setIncludeSchemas(self, schema_dict):
        """set the include schema dictionary, which is keyed with 
           schemaLocation (uri).  
           This is a means of providing 
           schemas to the current schema for content inclusion.
        """
        self._included_schemas = schema_dict

    def getIncludeSchemas(self):
        """get the include schema dictionary, which is keyed with 
           schemaLocation (uri). 
        """
        return self._included_schemas

    def getBaseUrl(self):
        """get base url, used for normalizing all relative uri's 
        """
        return self._base_url

    def setBaseUrl(self, url):
        """set base url, used for normalizing all relative uri's 
        """
        self._base_url = url

    def getElementFormDefault(self):
        """return elementFormDefault attribute
        """
        return self.attributes[XMLSchemaComponent.xsd]['elementFormDefault']

    def getAttributeFormDefault(self):
        """return attributeFormDefault attribute
        """
        return self.attributes[XMLSchemaComponent.xsd]['attributeFormDefault']

    def getBlockDefault(self):
        """return blockDefault attribute
        """
        return self.attributes[XMLSchemaComponent.xsd].get('blockDefault')

    def getFinalDefault(self):
        """return finalDefault attribute 
        """
        return self.attributes[XMLSchemaComponent.xsd].get('finalDefault')

    def load(self, node):
        self.setAttributes(node)
        self.targetNamespace = self.getTargetNamespace()
        contents = self.getContents(node)

        indx = 0
        num = len(contents)
        while indx < num:
            while indx < num:
                node = contents[indx]
                component = SplitQName(node.getTagName())[1]

                if component == 'include':
                    tp = self.__class__.Include(self)
                    tp.fromDom(node)
                    self.includes[tp.attributes['schemaLocation']] = tp

                    schema = tp.getSchema()
                    if schema.targetNamespace and \
                        schema.targetNamespace != self.targetNamespace:
                        raise SchemaError, 'included schema bad targetNamespace'

                    for collection in ['imports','elements','types',\
                        'attr_decl','attr_groups','model_groups','notations']:
                        for k,v in getattr(schema,collection).items():
                            if not getattr(self,collection).has_key(k):
                                setattr(self,collection,v)                             

                elif component == 'import':
                    tp = self.__class__.Import(self)
                    tp.fromDom(node)
                    if tp.attributes['namespace']:
                        if tp.attributes['namespace'] == self.targetNamespace:
                            raise SchemaError,\
                                'import and schema have same targetNamespace'
                        self.imports[tp.attributes['namespace']] = tp
                    else:
                        self.imports[self.__class__.empty_namespace] = tp
                elif component == 'redefine':
                    #print_debug('class %s, redefine skipped' %self.__class__, 5)
                    pass
                elif component == 'annotation':
                    #print_debug('class %s, annotation skipped' %self.__class__, 5)
                    pass
                else:
                    break
                indx += 1
            while indx < num:
                node = contents[indx]
                component = SplitQName(node.getTagName())[1]

                if component == 'complexType':
                    tp = ComplexType(self)
                    tp.fromDom(node)
                    self.types[tp.getAttribute('name')] = tp
                elif component == 'element':
                    tp = ElementDeclaration(self)
                    tp.fromDom(node)
                    self.elements[tp.getAttribute('name')] = tp
                elif component == 'simpleType':
                    tp = SimpleType(self)
                    tp.fromDom(node)
                    self.types[tp.getAttribute('name')] = tp
                elif component == 'group':
                    tp = ModelGroupDefinition(self)
                    tp.fromDom(node)
                    self.modelGroups[tp.getAttribute('name')] = tp
                elif component == 'notation':
                    tp = Notation(self)
                    tp.fromDom(node)
                    self.notations[tp.getAttribute('name')] = tp
                else:
                    break
                indx += 1

            while indx < num:
                node = contents[indx]
                component = SplitQName(node.getTagName())[1]

                if component == 'annotation':
                    #print_debug('class %s, annotation 2 skipped' %self.__class__, 5)
                    pass
                else:
                    break
                indx += 1


    class Import(XMLSchemaComponent):
        """<import> 
           parent:
               schema
           attributes:
               id -- ID
               namespace -- anyURI
               schemaLocation -- anyURI
           contents:
               annotation?
        """
        attributes = {'id':None,
            'namespace':None,
            'schemaLocation':None}
        contents = {'xsd':['annotation']}

        def __init__(self, parent):
            XMLSchemaComponent.__init__(self, parent)
            self.annotation = None
            self._schema = None

        def fromDom(self, node):
            self.setAttributes(node)
            contents = self.getContents(node)

            if self.attributes[XMLSchemaComponent.xsd]['namespace'] == self._parent().attributes[XMLSchemaComponent.xsd]['targetNamespace']:
                raise SchemaError, 'namespace of schema and import match'

            for i in contents:
                component = SplitQName(i.getTagName())[1]
                if component == 'annotation' and not self.annotation:
                    self.annotation = Annotation(self)
                    self.annotation.fromDom(i)
                else:
                    raise SchemaError, 'Unknown component (%s)' %(i.getTagName())

        def getSchema(self):
            """if schema is not defined, first look for a Schema class instance
               in parent Schema.  Else if not defined resolve schemaLocation
               and create a new Schema class instance, and keep a hard reference. 
            """
            if not self._schema:
                schema = self._parent().getImportSchemas().get(self.attributes[XMLSchemaComponent.xsd]['namespace'])
                if not schema and self._parent()._parent:
                    schema = self._parent()._parent().getImportSchemas().get(self.attributes[XMLSchemaComponent.xsd]['namespace'])
                if not schema:
                    if not self.attributes[XMLSchemaComponent.xsd].has_key('schemaLocation'):
                        raise SchemaError, 'namespace(%s) is unknown'\
                            %self.attributes[XMLSchemaComponent.xsd]['namespace']

                    url = urllib.basejoin(self._parent().getBaseUrl(),\
                           self.attributes[XMLSchemaComponent.xsd]['schemaLocation'])
                    reader = SchemaReader()
                    reader._imports = self._parent().getImportSchemas()
                    reader._includes = self._parent().getIncludeSchemas()
                    self._schema = reader.readFromUrl(url)
                    self._schema.setBaseUrl(url)
            return self._schema or schema


    class Include(XMLSchemaComponent):
        """<include schemaLocation>
           parent:
               schema
           attributes:
               id -- ID
               schemaLocation -- anyURI, required
           contents:
               annotation?
        """
        required = ['schemaLocation']
        attributes = {'id':None,
            'schemaLocation':None}
        contents = {'xsd':['annotation']}

        def __init__(self, parent):
            XMLSchemaComponent.__init__(self, parent)
            self.annotation = None
            self._schema = None

        def fromDom(self, node):
            self.setAttributes(node)
            contents = self.getContents(node)

            for i in contents:
                component = SplitQName(i.getTagName())[1]
                if component == 'annotation' and not self.annotation:
                    self.annotation = Annotation(self)
                    self.annotation.fromDom(i)
                else:
                    raise SchemaError, 'Unknown component (%s)' %(i.getTagName())

        def getSchema(self):
            """if schema is not defined, first look for a Schema class instance
               in parent Schema.  Else if not defined resolve schemaLocation
               and create a new Schema class instance.  
            """
            if not self._schema:
                schema = self._parent()._parent()
                self._schema = schema.getIncludeSchemas(\
                    self.attributes[XMLSchemaComponent.xsd]['schemaLocation'])
                if not self._schema:
                    url = BaseUriResolver().normalize(\
                       self.attributes[XMLSchemaComponent.xsd]['schemaLocation'], schema.getBaseUrl())
                    reader = SchemaReader()
                    reader._imports = schema.getImportSchemas()
                    reader._includes = schema.getIncludeSchemas()
                    self._schema = reader.readFromUrl(url)
                    self._schema.setBaseUrl(url)
            return self._schema


class AttributeDeclaration(XMLSchemaComponent,\
                           MarkerInterface,\
                           AttributeMarker,\
                           DeclarationMarker):
    """<attribute name>
       parent: 
           schema
       attributes:
           id -- ID
           name -- NCName, required
           type -- QName
           default -- string
           fixed -- string
       contents:
           annotation?, simpleType?
    """
    required = ['name']
    attributes = {'id':None,
        'name':None,
        'type':None,
        'default':None,
        'fixed':None}
    contents = {'xsd':['annotation','simpleType']}

    def __init__(self, parent):
        XMLSchemaComponent.__init__(self, parent)
        self.annotation = None
        self.content = None

    def fromDom(self, node):
        """ No list or union support
        """
        self.setAttributes(node)
        contents = self.getContents(node)

        for i in contents:
            component = SplitQName(i.getTagName())[1]
            if component == 'annotation' and not self.annotation:
                self.annotation = Annotation(self)
                self.annotation.fromDom(i)
            elif component == 'simpleType':
                self.content = SimpleType(self)
                self.content.fromDom(i)
            else:
                raise SchemaError, 'Unknown component (%s)' %(i.getTagName())


class LocalAttributeDeclaration(AttributeDeclaration,\
                                MarkerInterface,\
                                AttributeMarker,\
                                DeclarationMarker):
    """<attribute name>
       parent: 
           complexType, restriction, extension, attributeGroup
       attributes:
           id -- ID
           name -- NCName,  required
           type -- QName
           form -- ('qualified' | 'unqualified'), schema.attributeFormDefault
           use -- ('optional' | 'prohibited' | 'required'), optional
           default -- string
           fixed -- string
       contents:
           annotation?, simpleType?
    """
    required = ['name']
    attributes = {'id':None, 
        'name':None,
        'type':None,
        'form':lambda self: GetSchema(self).getAttributeFormDefault(),
        'use':'optional',
        'default':None,
        'fixed':None}
    contents = {'xsd':['annotation','simpleType']}

    def __init__(self, parent):
        AttributeDeclaration.__init__(self, parent)
        self.annotation = None
        self.content = None

    def fromDom(self, node):
        self.setAttributes(node)
        contents = self.getContents(node)

        for i in contents:
            component = SplitQName(i.getTagName())[1]
            if component == 'annotation' and not self.annotation:
                self.annotation = Annotation(self)
                self.annotation.fromDom(i)
            elif component == 'simpleType':
                self.content = SimpleType(self)
                self.content.fromDom(i)
            else:
                raise SchemaError, 'Unknown component (%s)' %(i.getTagName())


class AttributeWildCard(XMLSchemaComponent,\
                        MarkerInterface,\
                        AttributeMarker,\
                        DeclarationMarker,\
                        WildCardMarker):
    """<anyAttribute>
       parents: 
           complexType, restriction, extension, attributeGroup
       attributes:
           id -- ID
           namespace -- '##any' | '##other' | 
                        (anyURI* | '##targetNamespace' | '##local'), ##any
           processContents -- 'lax' | 'skip' | 'strict', strict
       contents:
           annotation?
    """
    attributes = {'id':None, 
        'namespace':'##any',
        'processContents':'strict'}
    contents = {'xsd':['annotation']}

    def __init__(self, parent):
        XMLSchemaComponent.__init__(self, parent)
        self.annotation = None

    def fromDom(self, node):
        self.setAttributes(node)
        contents = self.getContents(node)

        for i in contents:
            component = SplitQName(i.getTagName())[1]
            if component == 'annotation' and not self.annotation:
                self.annotation = Annotation(self)
                self.annotation.fromDom(i)
            else:
                raise SchemaError, 'Unknown component (%s)' %(i.getTagName())


class AttributeReference(XMLSchemaComponent,\
                         MarkerInterface,\
                         AttributeMarker,\
                         ReferenceMarker):
    """<attribute ref>
       parents: 
           complexType, restriction, extension, attributeGroup
       attributes:
           id -- ID
           ref -- QName, required
           use -- ('optional' | 'prohibited' | 'required'), optional
           default -- string
           fixed -- string
       contents:
           annotation?
    """
    required = ['ref']
    attributes = {'id':None, 
        'ref':None,
        'use':'optional',
        'default':None,
        'fixed':None}
    contents = {'xsd':['annotation']}

    def __init__(self, parent):
        XMLSchemaComponent.__init__(self, parent)
        self.annotation = None

    def fromDom(self, node):
        self.setAttributes(node)
        contents = self.getContents(node)

        for i in contents:
            component = SplitQName(i.getTagName())[1]
            if component == 'annotation' and not self.annotation:
                self.annotation = Annotation(self)
                self.annotation.fromDom(i)
            else:
                raise SchemaError, 'Unknown component (%s)' %(i.getTagName())


class AttributeGroupDefinition(XMLSchemaComponent,\
                               MarkerInterface,\
                               AttributeGroupMarker,\
                               DefinitionMarker):
    """<attributeGroup name>
       parents: 
           schema, redefine
       attributes:
           id -- ID
           name -- NCName,  required
       contents:
           annotation?
    """
    required = ['name']
    attributes = {'id':None, 
        'name':None}
    contents = {'xsd':['annotation']}

    def __init__(self, parent):
        XMLSchemaComponent.__init__(self, parent)
        self.annotation = None

    def fromDom(self, node):
        self.setAttributes(node)
        contents = self.getContents(node)

        for i in contents:
            component = SplitQName(i.getTagName())[1]
            if component == 'annotation' and not self.annotation:
                self.annotation = Annotation(self)
                self.annotation.fromDom(i)
            else:
                raise SchemaError, 'Unknown component (%s)' %(i.getTagName())


class AttributeGroupReference(XMLSchemaComponent,\
                              MarkerInterface,\
                              AttributeGroupMarker,\
                              ReferenceMarker):
    """<attributeGroup ref>
       parents: 
           complexType, restriction, extension, attributeGroup
       attributes:
           id -- ID
           ref -- QName, required
       contents:
           annotation?
    """
    required = ['ref']
    attributes = {'id':None, 
        'ref':None}
    contents = {'xsd':['annotation']}

    def __init__(self, parent):
        XMLSchemaComponent.__init__(self, parent)
        self.annotation = None

    def fromDom(self, node):
        self.setAttributes(node)
        contents = self.getContents(node)

        for i in contents:
            component = SplitQName(i.getTagName())[1]
            if component == 'annotation' and not self.annotation:
                self.annotation = Annotation(self)
                self.annotation.fromDom(i)
            else:
                raise SchemaError, 'Unknown component (%s)' %(i.getTagName())



######################################################
# Elements
#####################################################
class IdentityConstrants(XMLSchemaComponent):
    """Allow one to uniquely identify nodes in a document and ensure the 
       integrity of references between them.

       attributes -- dictionary of attributes
       selector -- XPath to selected nodes
       fields -- list of XPath to key field
    """
    def __init__(self, parent):
        XMLSchemaComponent.__init__(self, parent)
        self.selector = None
        self.fields = None
        self.annotation = None

    def fromDom(node):
        self.setAttributes(node)
        contents = self.getContents(node)
        fields = []

        for i in contents:
            component = SplitQName(i.getTagName())[1]
            if component in self.__class__.contents['xsd']:
                if component == 'annotation' and not self.annotation:
                    self.annotation = Annotation(self)
                    self.annotation.fromDom(i)
                elif component == 'selector':
                    self.selector = self.Selector(self)
                    self.selector.fromDom(i)
                    continue
                elif component == 'field':
                    fields.append(self.Field(self))
                    fields[-1].fromDom(i)
                    continue
                else:
                    raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
            else:
                raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
            self.fields = tuple(fields)


    class Constraint(XMLSchemaComponent):
        def __init__(self, parent):
            XMLSchemaComponent.__init__(self, parent)
            self.annotation = None

        def fromDom(node):
            self.setAttributes(node)
            contents = self.getContents(node)

            for i in contents:
                component = SplitQName(i.getTagName())[1]
                if component in self.__class__.contents['xsd']:
                    if component == 'annotation' and not self.annotation:
                        self.annotation = Annotation(self)
                        self.annotation.fromDom(i)
                    else:
                        raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
                else:
                    raise SchemaError, 'Unknown component (%s)' %(i.getTagName())

    class Selector(Constraint):
        """<selector xpath>
           parent: 
               unique, key, keyref
           attributes:
               id -- ID
               xpath -- XPath subset,  required
           contents:
               annotation?
        """
        required = ['xpath']
        attributes = {'id':None, 
            'xpath':None}
        contents = {'xsd':['annotation']}

    class Field(Constraint): 
        """<field xpath>
           parent: 
               unique, key, keyref
           attributes:
               id -- ID
               xpath -- XPath subset,  required
           contents:
               annotation?
        """
        required = ['xpath']
        attributes = {'id':None, 
            'xpath':None}
        contents = {'xsd':['annotation']}


class Unique(IdentityConstrants):
    """<unique name> Enforce fields are unique w/i a specified scope.

       parent: 
           element
       attributes:
           id -- ID
           name -- NCName,  required
       contents:
           annotation?, selector, field+
    """
    required = ['name']
    attributes = {'id':None, 
        'name':None}
    contents = {'xsd':['annotation', 'selector', 'field']}


class Key(IdentityConstrants):
    """<key name> Enforce fields are unique w/i a specified scope, and all
           field values are present w/i document.  Fields cannot
           be nillable.

       parent: 
           element
       attributes:
           id -- ID
           name -- NCName,  required
       contents:
           annotation?, selector, field+
    """
    required = ['name']
    attributes = {'id':None, 
        'name':None}
    contents = {'xsd':['annotation', 'selector', 'field']}


class KeyRef(IdentityConstrants):
    """<keyref name refer> Ensure a match between two sets of values in an 
           instance.
       parent: 
           element
       attributes:
           id -- ID
           name -- NCName,  required
           refer -- QName,  required
       contents:
           annotation?, selector, field+
    """
    required = ['name', 'refer']
    attributes = {'id':None, 
        'name':None,
        'refer':None}
    contents = {'xsd':['annotation', 'selector', 'field']}


class ElementDeclaration(XMLSchemaComponent,\
                         MarkerInterface,\
                         ElementMarker,\
                         DeclarationMarker):
    """<element name>
       parents:
           schema
       attributes:
           id -- ID
           name -- NCName,  required
           type -- QName
           default -- string
           fixed -- string
           nillable -- boolean,  false
           abstract -- boolean,  false
           substitutionGroup -- QName
           block -- ('#all' | ('substition' | 'extension' | 'restriction')*), 
               schema.blockDefault 
           final -- ('#all' | ('extension' | 'restriction')*), 
               schema.finalDefault 
       contents:
           annotation?, (simpleType,complexType)?, (key | keyref | unique)*
           
    """
    required = ['name']
    attributes = {'id':None, 
        'name':None,
        'type':None,
        'default':None,
        'fixed':None,
        'nillable':0,
        'abstract':0,
        'block':lambda self: self._parent().getBlockDefault(),
        'final':lambda self: self._parent().getFinalDefault()}
    contents = {'xsd':['annotation', 'simpleType', 'complexType', 'key',\
        'keyref', 'unique']}

    def __init__(self, parent):
        XMLSchemaComponent.__init__(self, parent)
        self.annotation = None
        self.content = None
        self.constraints = None

    def fromDom(self, node):
        self.setAttributes(node)
        contents = self.getContents(node)
        constraints = []

        for i in contents:
            component = SplitQName(i.getTagName())[1]
            if component in self.__class__.contents['xsd']:
                if component == 'annotation' and not self.annotation:
                    self.annotation = Annotation(self)
                    self.annotation.fromDom(i)
                elif component == 'simpleType' and not self.content:
	            self.content = AnonymousSimpleType(self)
                    self.content.fromDom(i)
                elif component == 'complexType' and not self.content:
	            self.content = LocalComplexType(self)
                    self.content.fromDom(i)
                elif component == 'key':
	            constraints.append(Key(self))
	            constraints[-1].fromDom(i)
                elif component == 'keyref':
	            constraints.append(KeyRef(self))
	            constraints[-1].fromDom(i)
                elif component == 'unique':
	            constraints.append(Unique(self))
	            constraints[-1].fromDom(i)
                else:
	            raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
            else:
	        raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
        self.constraints = tuple(constraints)


class LocalElementDeclaration(ElementDeclaration,\
                              MarkerInterface,\
                              ElementMarker,\
                              DeclarationMarker):
    """<element>
       parents:
           all, choice, sequence
       attributes:
           id -- ID
           name -- NCName,  required
           form -- ('qualified' | 'unqualified'), schema.elementFormDefault
           type -- QName
           minOccurs -- Whole Number, 1
           maxOccurs -- (Whole Number | 'unbounded'), 1
           default -- string
           fixed -- string
           nillable -- boolean,  false
           block -- ('#all' | ('extension' | 'restriction')*), schema.blockDefault 
       contents:
           annotation?, (simpleType,complexType)?, (key | keyref | unique)*
    """
    required = ['name']
    attributes = {'id':None, 
        'name':None,
        'form':lambda self: GetSchema(self).getElementFormDefault(),
        'type':None,
        'minOccurs':'1',
        'maxOccurs':'1',
        'default':None,
        'fixed':None,
        'nillable':0,
        'abstract':0,
        'block':lambda self: GetSchema(self).getBlockDefault()}
    contents = {'xsd':['annotation', 'simpleType', 'complexType', 'key',\
        'keyref', 'unique']}


class ElementReference(ElementDeclaration,\
                       MarkerInterface,\
                       ElementMarker,\
                       ReferenceMarker):
    """<element ref>
       parents: 
           all, choice, sequence
       attributes:
           id -- ID
           ref -- QName, required
           minOccurs -- Whole Number, 1
           maxOccurs -- (Whole Number | 'unbounded'), 1
       contents:
           annotation?
    """
    required = ['ref']
    attributes = {'id':None, 
        'ref':None,
        'minOccurs':'1',
        'maxOccurs':'1'}
    contents = {'xsd':['annotation']}

 
class ElementWildCard(LocalElementDeclaration,\
                      MarkerInterface,\
                      ElementMarker,\
                      DeclarationMarker,\
                      WildCardMarker):
    """<any>
       parents: 
           choice, sequence
       attributes:
           id -- ID
           minOccurs -- Whole Number, 1
           maxOccurs -- (Whole Number | 'unbounded'), 1
           namespace -- '##any' | '##other' | 
                        (anyURI* | '##targetNamespace' | '##local'), ##any
           processContents -- 'lax' | 'skip' | 'strict', strict
       contents:
           annotation?
    """
    required = []
    attributes = {'id':None, 
        'minOccurs':'1',
        'maxOccurs':'1',
        'namespace':'##any',
        'processContents':'strict'}
    contents = {'xsd':['annotation']}


######################################################
# Model Groups
#####################################################
class Sequence(XMLSchemaComponent,\
               MarkerInterface,\
               ModelGroupMarker):
    """<sequence>
       parents: 
           complexType, extension, restriction, group, choice, sequence
       attributes:
           id -- ID
           minOccurs -- Whole Number, 1
           maxOccurs -- (Whole Number | 'unbounded'), 1

       contents:
           annotation?, (element | group | choice | sequence | any)*
    """
    attributes = {'id':None, 
        'minOccurs':'1',
        'maxOccurs':'1'}
    contents = {'xsd':['annotation', 'element', 'group', 'choice', 'sequence',\
         'any']}

    def __init__(self, parent):
        XMLSchemaComponent.__init__(self, parent)
        self.annotation = None
        self.content = None

    def fromDom(self, node):
        self.setAttributes(node)
        contents = self.getContents(node)
        content = []

        for i in contents:
            component = SplitQName(i.getTagName())[1]
            if component in self.__class__.contents['xsd']:
                if component == 'annotation' and not self.annotation:
                    self.annotation = Annotation(self)
                    self.annotation.fromDom(i)
                    continue
                elif component == 'element':
                    if i.hasattr('ref'):
	                content.append(ElementReference(self))
                    else:
	                content.append(LocalElementDeclaration(self))
                elif component == 'group':
	            content.append(ModelGroupReference(self))
                elif component == 'choice':
	            content.append(Choice(self))
                elif component == 'sequence':
	            content.append(Sequence(self))
                elif component == 'any':
	            content.append(ElementWildCard(self))
                else:
	            raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
                content[-1].fromDom(i)
            else:
	        raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
        self.content = tuple(content)


class All(XMLSchemaComponent,\
          MarkerInterface,\
          ModelGroupMarker):
    """<all>
       parents: 
           complexType, extension, restriction, group
       attributes:
           id -- ID
           minOccurs -- '0' | '1', 1
           maxOccurs -- '1', 1

       contents:
           annotation?, element*
    """
    attributes = {'id':None, 
        'minOccurs':'1',
        'maxOccurs':'1'}
    contents = {'xsd':['annotation', 'element']}

    def __init__(self, parent):
        XMLSchemaComponent.__init__(self, parent)
        self.annotation = None
        self.content = None

    def fromDom(self, node):
        self.setAttributes(node)
        contents = self.getContents(node)
        content = []

        for i in contents:
            component = SplitQName(i.getTagName())[1]
            if component in self.__class__.contents['xsd']:
                if component == 'annotation' and not self.annotation:
                    self.annotation = Annotation(self)
                    self.annotation.fromDom(i)
                    continue
                elif component == 'element':
                    if i.hasattr('ref'):
	                content.append(ElementReference(self))
                    else:
	                content.append(LocalElementDeclaration(self))
                else:
	            raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
                content[-1].fromDom(i)
            else:
	        raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
        self.content = tuple(content)


class Choice(XMLSchemaComponent,\
             MarkerInterface,\
             ModelGroupMarker):
    """<choice>
       parents: 
           complexType, extension, restriction, group, choice, sequence
       attributes:
           id -- ID
           minOccurs -- Whole Number, 1
           maxOccurs -- (Whole Number | 'unbounded'), 1

       contents:
           annotation?, (element | group | choice | sequence | any)*
    """
    attributes = {'id':None, 
        'minOccurs':'1',
        'maxOccurs':'1'}
    contents = {'xsd':['annotation', 'element', 'group', 'choice', 'sequence',\
         'any']}

    def __init__(self, parent):
        XMLSchemaComponent.__init__(self, parent)
        self.annotation = None
        self.content = None

    def fromDom(self, node):
        self.setAttributes(node)
        contents = self.getContents(node)
        content = []

        for i in contents:
            component = SplitQName(i.getTagName())[1]
            if component in self.__class__.contents['xsd']:
                if component == 'annotation' and not self.annotation:
                    self.annotation = Annotation(self)
                    self.annotation.fromDom(i)
                    continue
                elif component == 'element':
                    if i.hasattr('ref'):
	                content.append(ElementReference(self))
                    else:
	                content.append(LocalElementDeclaration(self))
                elif component == 'group':
	            content.append(ModelGroupReference(self))
                elif component == 'choice':
	            content.append(Choice(self))
                elif component == 'sequence':
	            content.append(Sequence(self))
                elif component == 'any':
	            content.append(ElementWildCard(self))
                else:
	            raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
                content[-1].fromDom(i)
            else:
	        raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
        self.content = tuple(content)


class ModelGroupDefinition(XMLSchemaComponent,\
                           MarkerInterface,\
                           ModelGroupMarker,\
                           DefinitionMarker):
    """<group name>
       parents:
           redefine, schema
       attributes:
           id -- ID
           name -- NCName,  required

       contents:
           annotation?, (all | choice | sequence)?
    """
    required = ['name']
    attributes = {'id':None, 
        'name':None}
    contents = {'xsd':['annotation', 'all', 'choice', 'sequence']}

    def __init__(self, parent):
        XMLSchemaComponent.__init__(self, parent)
        self.annotation = None
        self.content = None

    def fromDom(self, node):
        self.setAttributes(node)
        contents = self.getContents(node)

        for i in contents:
            component = SplitQName(i.getTagName())[1]
            if component in self.__class__.contents['xsd']:
                if component == 'annotation' and not self.annotation:
                    self.annotation = Annotation()
                    self.annotation.fromDom(i)
                    continue
                elif component == 'all' and not self.content:
                    self.content = All(self)
                elif component == 'choice' and not self.content:
                    self.content = Choice(self)
                elif component == 'sequence' and not self.content:
                    self.content = Sequence(self)
                else:
	            raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
                self.content.fromDom(i)
            else:
	        raise SchemaError, 'Unknown component (%s)' %(i.getTagName())


class ModelGroupReference(XMLSchemaComponent,\
                          MarkerInterface,\
                          ModelGroupMarker,\
                          ReferenceMarker):
    """<group ref>
       parents:
           choice, complexType, extension, restriction, sequence
       attributes:
           id -- ID
           ref -- NCName,  required

       contents:
           annotation?
    """
    required = ['ref']
    attributes = {'id':None, 
        'ref':None}
    contents = {'xsd':['annotation']}

    def __init__(self, parent):
        XMLSchemaComponent.__init__(self, parent)
        self.annotation = None

    def fromDom(self, node):
        self.setAttributes(node)
        contents = self.getContents(node)

        for i in contents:
            component = SplitQName(i.getTagName())[1]
            if component in self.__class__.contents['xsd']:
                if component == 'annotation' and not self.annotation:
                    self.annotation = Annotation(self)
                    self.annotation.fromDom(i)
                else:
	            raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
            else:
	        raise SchemaError, 'Unknown component (%s)' %(i.getTagName())



class ComplexType(XMLSchemaComponent,\
                  MarkerInterface,\
                  DefinitionMarker,\
                  ComplexMarker):
    """<complexType name>
       parents:
           redefine, schema
       attributes:
           id -- ID
           name -- NCName,  required
           mixed -- boolean, false
           abstract -- boolean,  false
           block -- ('#all' | ('extension' | 'restriction')*), schema.blockDefault 
           final -- ('#all' | ('extension' | 'restriction')*), schema.finalDefault 

       contents:
           annotation?, (simpleContent | complexContent | 
           ((group | all | choice | sequence)?, (attribute | attributeGroup)*, anyAttribute?))
    """
    required = ['name']
    attributes = {'id':None, 
        'name':None,
        'mixed':0,
        'abstract':0,
        'block':lambda self: self._parent().getBlockDefault(),
        'final':lambda self: self._parent().getFinalDefault()}
    contents = {'xsd':['annotation', 'simpleContent', 'complexContent',\
        'group', 'all', 'choice', 'sequence', 'attribute', 'attributeGroup',\
        'anyAttribute', 'any']}

    def __init__(self, parent):
        XMLSchemaComponent.__init__(self, parent)
        self.annotation = None
        self.content = None
        self.attr_content = None

    def fromDom(self, node):
        self.setAttributes(node)
        contents = self.getContents(node)
      
        indx = 0
        num = len(contents)
        #XXX ugly
        if not num:
            return
        component = SplitQName(contents[indx].getTagName())[1]
        if component == 'annotation':
            self.annotation = Annotation(self)
            self.annotation.fromDom(contents[indx])
            indx += 1
            component = SplitQName(contents[indx].getTagName())[1]

        self.content = None
        if component == 'simpleContent':
            self.content = self.__class__.SimpleContent(self)
            self.content.fromDom(contents[indx])
        elif component == 'complexContent':
            self.content = self.__class__.ComplexContent(self)
            self.content.fromDom(contents[indx])
        else:
            if component == 'all':
                self.content = All(self)
            elif component == 'choice':
                self.content = Choice(self)
            elif component == 'sequence':
                self.content = Sequence(self)
            elif component == 'group':
                self.content = ModelGroupReference(self)

            if self.content:
                self.content.fromDom(contents[indx])
                indx += 1

            self.attr_content = []
            while indx < num:
                component = SplitQName(contents[indx].getTagName())[1]
                if component == 'attribute':
                    if contents[indx].hasattr('ref'):
                        self.attr_content.append(AttributeReference(self))
                    else:
                        self.attr_content.append(LocalAttributeDeclaration(self))
                elif component == 'attributeGroup':
                    self.attr_content.append(AttributeGroupDefinition(self))
                elif component == 'anyAttribute':
                    self.attr_content.append(AttributeWildCard(self))
                else:
	            raise SchemaError, 'Unknown component (%s)' %(contents[indx].getTagName())
                self.attr_content[-1].fromDom(contents[indx])
                indx += 1

    class _DerivedType(XMLSchemaComponent):
	def __init__(self, parent):
            XMLSchemaComponent.__init__(self, parent)
            self.annotation = None
            self.derivation = None

        def fromDom(self, node):
            self.setAttributes(node)
            contents = self.getContents(node)

            for i in contents:
                component = SplitQName(i.getTagName())[1]
                if component in self.__class__.contents['xsd']:
                    if component == 'annotation' and not self.annotation:
                        self.annotation = Annotation(self)
                        self.annotation.fromDom(i)
                        continue
                    elif component == 'restriction' and not self.derivation:
                        self.derivation = self.__class__.Restriction(self)
                    elif component == 'extension' and not self.derivation:
                        self.derivation = self.__class__.Extension(self)
                    else:
	                raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
                else:
	            raise SchemaError, 'Unknown component (%s)' %(i.getTagName())
                self.derivation.fromDom(i)

    class ComplexContent(_DerivedType,\
                         MarkerInterface,\
                         ComplexMarker):
        """<complexContent>
           parents:
               complexType
           attributes:
               id -- ID
               mixed -- boolean, false

           contents:
               annotation?, (restriction | extension)
        """
        attributes = {'id':None, 
            'mixed':0 }
        contents = {'xsd':['annotation', 'restriction', 'extension']}

        class _DerivationBase(XMLSchemaComponent):
            """<extension>,<restriction>
               parents:
                   complexContent
               attributes:
                   id -- ID
                   base -- QName, required

               contents:
                   annotation?, (group | all | choice | sequence)?, 
                       (attribute | attributeGroup)*, anyAttribute?
            """
            required = ['base']
            attributes = {'id':None, 
                'base':None }
            contents = {'xsd':['annotation', 'group', 'all', 'choice',\
                'sequence', 'attribute', 'attributeGroup', 'anyAttribute']}

            def fromDom(self, node):
                self.setAttributes(node)
                contents = self.getContents(node)

                indx = 0
                num = len(contents)
                #XXX ugly
                if not num:
                    return
                component = SplitQName(contents[indx].getTagName())[1]
                if component == 'annotation':
                    self.annotation = Annotation(self)
                    self.annotation.fromDom(contents[indx])
                    indx += 1
                    component = SplitQName(contents[indx].getTagName())[1]

                if component == 'all':
                    self.content = All(self)
                    self.content.fromDom(contents[indx])
                    indx += 1
                elif component == 'choice':
                    self.content = Choice(self)
                    self.content.fromDom(contents[indx])
                    indx += 1
                elif component == 'sequence':
                    self.content = Sequence(self)
                    self.content.fromDom(contents[indx])
                    indx += 1
                elif component == 'group':
                    self.content = ModelGroupReference(self)
                    self.content.fromDom(contents[indx])
                    indx += 1
                else:
	            self.content = None

                self.attr_content = []
                while indx < num:
                    component = SplitQName(contents[indx].getTagName())[1]
                    if component == 'attribute':
                        if contents[indx].hasattr('ref'):
                            self.attr_content.append(AttributeReference(self))
                        else:
                            self.attr_content.append(LocalAttributeDeclaration(self))
                    elif component == 'attributeGroup':
                        self.attr_content.append(AttributeGroupDefinition(self))
                    elif component == 'anyAttribute':
                        self.attr_content.append(AttributeWildCard(self))
                    else:
	                raise SchemaError, 'Unknown component (%s)' %(contents[indx].getTagName())
                    self.attr_content[-1].fromDom(contents[indx])
                    indx += 1

        class Extension(_DerivationBase, MarkerInterface, ExtensionMarker):
            """<extension base>
               parents:
                   complexContent
               attributes:
                   id -- ID
                   base -- QName, required

               contents:
                   annotation?, (group | all | choice | sequence)?, 
                       (attribute | attributeGroup)*, anyAttribute?
            """
            pass

        class Restriction(_DerivationBase,\
                          MarkerInterface,\
                          RestrictionMarker):
            """<restriction base>
               parents:
                   complexContent
               attributes:
                   id -- ID
                   base -- QName, required

               contents:
                   annotation?, (group | all | choice | sequence)?, 
                       (attribute | attributeGroup)*, anyAttribute?
            """
            pass


    class SimpleContent(_DerivedType,\
                        MarkerInterface,\
                        SimpleMarker):
        """<simpleContent>
           parents:
               complexType
           attributes:
               id -- ID

           contents:
               annotation?, (restriction | extension)
        """
        attributes = {'id':None}
        contents = {'xsd':['annotation', 'restriction', 'extension']}

        class Extension(XMLSchemaComponent,\
                        MarkerInterface,\
                        ExtensionMarker):
            """<extension base>
               parents:
                   simpleContent
               attributes:
                   id -- ID
                   base -- QName, required

               contents:
                   annotation?, (group | all | choice | sequence)?, 
                       (attribute | attributeGroup)*, anyAttribute?
            """
            required = ['base']
            attributes = {'id':None, 
                'base':None }
            contents = {'xsd':['annotation', 'group', 'all', 'choice',\
                'sequence', 'attribute', 'attributeGroup', 'anyAttribute']}

            def fromDom(self, node):
                self.setAttributes(node)
                contents = self.getContents(node)

                indx = 0
                num = len(contents)
                component = SplitQName(contents[indx].getTagName())[1]
                if component == 'annotation':
                    self.annotation = Annotation(self)
                    self.annotation.fromDom(contents[indx])
                    indx += 1
                    component = SplitQName(contents[indx].getTagName())[1]

                if component == 'all':
                    self.content = All(self)
                elif component == 'choice':
                    self.content = Choice(self)
                elif component == 'sequence':
                    self.content = Sequence(self)
                elif component == 'group':
                    self.content = ModelGroupReference(self)
                else:
	            raise SchemaError, 'Unknown component (%s)' %(contents[indx].getTagName())

                self.content.fromDom(contents[indx])
                indx += 1
                self.attr_content = []
                while indx < num:
                    component = SplitQName(contents[indx].getTagName())[1]
                    if component == 'attribute':
                        if contents[indx].hasattr('ref'):
                            self.attr_content.append(AttributeReference(self))
                        else:
                            self.attr_content.append(LocalAttributeDeclaration(self))
                    elif component == 'attributeGroup':
                        self.attr_content.append(AttributeGroupDefinition(self))
                    elif component == 'anyAttribute':
                        self.attr_content.append(AttributeWildCard(self))
                    else:
	                raise SchemaError, 'Unknown component (%s)' %(contents[indx].getTagName())
                    self.attr_content[-1].fromDom(contents[indx])
                    indx += 1


        class Restriction(XMLSchemaComponent,\
                          MarkerInterface,\
                          RestrictionMarker):
            """<restriction base>
               parents:
                   simpleContent
               attributes:
                   id -- ID
                   base -- QName, required

               contents:
                   annotation?, simpleType?, (enumeration | length | 
                   maxExclusive | maxInclusive | maxLength | minExclusive | 
                   minInclusive | minLength | pattern | fractionDigits | 
                   totalDigits | whiteSpace)*, (attribute | attributeGroup)*, 
                   anyAttribute?
            """
            required = ['base']
            attributes = {'id':None, 
                'base':None }
            contents = {'xsd':['annotation', 'simpleType', 'attribute',\
                'attributeGroup', 'anyAttribute'] + RestrictionMarker.facets}


class LocalComplexType(ComplexType):
    """<complexType>
       parents:
           element
       attributes:
           id -- ID
           mixed -- boolean, false

       contents:
           annotation?, (simpleContent | complexContent | 
           ((group | all | choice | sequence)?, (attribute | attributeGroup)*, anyAttribute?))
    """
    required = []
    attributes = {'id':None, 
        'mixed':0}
    

class SimpleType(XMLSchemaComponent,\
                 MarkerInterface,\
                 DefinitionMarker,\
                 SimpleMarker):
    """<simpleType name>
       parents:
           redefine, schema
       attributes:
           id -- ID
           name -- NCName, required
           final -- ('#all' | ('extension' | 'restriction' | 'list' | 'union')*), 
               schema.finalDefault 

       contents:
           annotation?, (restriction | list | union)
    """
    required = ['name']
    attributes = {'id':None,
        'name':None,
        'final':lambda self: self._parent().getFinalDefault()}
    contents = {'xsd':['annotation', 'restriction', 'list', 'union']}

    def __init__(self, parent):
        XMLSchemaComponent.__init__(self, parent)
        self.annotation = None
        self.content = None
        self.attr_content = None

    def fromDom(self, node):
        self.setAttributes(node)
        contents = self.getContents(node)
        for child in contents:
            component = SplitQName(child.getTagName())[1]
            if component == 'annotation':
                self.annotation = Annotation(self)
                self.annotation.fromDom(child)
            break
        else:
            return
        if component == 'restriction':
            self.content = self.__class__.Restriction(self)
        elif component == 'list':
            self.content = self.__class__.List(self)
        elif component == 'union':
            self.content = self.__class__.Union(self)
        else:
            raise SchemaError, 'Unknown component (%s)' %(contents[indx].getTagName())
        self.content.fromDom(child)

    class Restriction(XMLSchemaComponent,\
                      MarkerInterface,\
                      RestrictionMarker):
        """<restriction base>
           parents:
               simpleType
           attributes:
               id -- ID
               base -- QName, required or simpleType child

           contents:
               annotation?, simpleType?, (enumeration | length | 
               maxExclusive | maxInclusive | maxLength | minExclusive | 
               minInclusive | minLength | pattern | fractionDigits | 
               totalDigits | whiteSpace)*
        """
        attributes = {'id':None, 
            'base':None }
        contents = {'xsd':['annotation', 'simpleType']+RestrictionMarker.facets}

        def __init__(self, parent):
            XMLSchemaComponent.__init__(self, parent)
            self.annotation = None
            self.content = None
            self.attr_content = None

        def fromDom(self, node):
            self.setAttributes(node)
            contents = self.getContents(node)
            self.content = []
            self.attr_content = []

            for indx in range(len(contents)):
                component = SplitQName(contents[indx].getTagName())[1]
                if (component == 'annotation') and (not indx):
                    self.annotation = Annotation(self)
                    self.annotation.fromDom(contents[indx])
                    continue
                elif (component == 'simpleType') and (not indx or indx == 1):
                    self.content.append(SimpleType(self))
                    self.content[-1].fromDom(contents[indx])
                elif component in RestrictionMarker.facets:
                    #print_debug('%s class instance, skipping %s' %(self.__class__, component))
                    pass
                else:
                    raise SchemaError, 'Unknown component (%s)' %(i.getTagName())


    class Union(XMLSchemaComponent):
        """<union>
           parents:
               simpleType
           attributes:
               id -- ID
               memberTypes -- list of QNames, required or simpleType child.

           contents:
               annotation?, simpleType*
        """
        attributes = {'id':None, 
            'memberTypes':None }
        contents = {'xsd':['annotation', 'simpleType']}

    class List(XMLSchemaComponent):
        """<union>
           parents:
               simpleType
           attributes:
               id -- ID
               itemType -- QName, required or simpleType child.

           contents:
               annotation?, simpleType?
        """
        attributes = {'id':None, 
            'memberTypes':None }
        contents = {'xsd':['annotation', 'simpleType']}

                 
class AnonymousSimpleType(SimpleType,\
                          MarkerInterface,\
                          SimpleMarker):
    """<simpleType>
       parents:
           attribute, element, list, restriction, union
       attributes:
           id -- ID

       contents:
           annotation?, (restriction | list | union)
    """
    required = []
    attributes = {'id':None}


class Redefine:
    """<redefine>
       parents:
       attributes:

       contents:
    """
    pass

###########################
###########################


if sys.version_info[:2] >= (2, 2):
    tupleClass = tuple
else:
    import UserTuple
    tupleClass = UserTuple.UserTuple

class TypeDescriptionComponent(tupleClass):
    """Tuple of length 2, consisting of
       a namespace and unprefixed name.
    """
    def __init__(self, args):
        """args -- (namespace, name)
           Remove the name's prefix, irrelevant.
        """
        if len(args) != 2:
            raise TypeError, 'expecting tuple (namespace, name), got %s' %args
        elif args[1].find(':') >= 0:
            args = (args[0], SplitQName(args[1])[1])
        tuple.__init__(self, args)
        return

    def getTargetNamespace(self):
        return self[0]

    def getName(self):
        return self[1]


'''
import string, types, base64, re
from Utility import DOM, Collection
from StringIO import StringIO


class SchemaReader:
    """A SchemaReader creates XMLSchema objects from urls and xml data."""

    def loadFromStream(self, file):
        """Return an XMLSchema instance loaded from a file object."""
        document = DOM.loadDocument(file)
        schema = XMLSchema()
        schema.load(document)
        return schema

    def loadFromString(self, data):
        """Return an XMLSchema instance loaded from an xml string."""
        return self.loadFromStream(StringIO(data))

    def loadFromURL(self, url):
        """Return an XMLSchema instance loaded from the given url."""
        document = DOM.loadFromURL(url)
        schema = XMLSchema()
        schema.location = url
        schema.load(document)
        return schema

    def loadFromFile(self, filename):
        """Return an XMLSchema instance loaded from the given file."""
        file = open(filename, 'rb')
        try:     schema = self.loadFromStream(file)
        finally: file.close()
        return schema

class SchemaError(Exception):
    pass

class XMLSchema:
    # This is temporary, for the benefit of WSDL until the real thing works.
    def __init__(self, element):
        self.targetNamespace = DOM.getAttr(element, 'targetNamespace')
        self.element = element

class realXMLSchema:
    """A schema is a collection of schema components derived from one
       or more schema documents, that is, one or more <schema> element
       information items. It represents the abstract notion of a schema
       rather than a single schema document (or other representation)."""
    def __init__(self):
        self.simpleTypes = Collection(self)
        self.complexTypes = Collection(self)
        self.attributes = Collection(self)
        self.elements = Collection(self)
        self.attrGroups = Collection(self)
        self.idConstraints=None
        self.modelGroups = None
        self.notations = None
        self.extensions = []

    targetNamespace = None
    attributeFormDefault = 'unqualified'
    elementFormDefault = 'unqualified'
    blockDefault = None
    finalDefault = None
    location = None
    version = None
    id = None

    def load(self, document):
        if document.nodeType == document.DOCUMENT_NODE:
            schema = DOM.getElement(document, 'schema', None, None)
        else:
            schema = document
        if schema is None:
            raise SchemaError('Missing <schema> element.')

        self.namespace = namespace = schema.namespaceURI
        if not namespace in DOM.NS_XSD_ALL:
            raise SchemaError(
                'Unknown XML schema namespace: %s.' % self.namespace
                )

        for attrname in (
            'targetNamespace', 'attributeFormDefault', 'elementFormDefault',
            'blockDefault', 'finalDefault', 'version', 'id'
            ):
            value = DOM.getAttr(schema, attrname, None, None)
            if value is not None:
                setattr(self, attrname, value)


        # Resolve imports and includes here?
##         imported = {}
##         while 1:
##             imports = []
##             for element in DOM.getElements(definitions, 'import', NS_WSDL):
##                 location = DOM.getAttr(element, 'location')
##                 if not imported.has_key(location):
##                     imports.append(element)
##             if not imports:
##                 break
##             for element in imports:
##                 self._import(document, element)
##                 imported[location] = 1

        for element in DOM.getElements(schema, None, None):
            localName = element.localName

            if not DOM.nsUriMatch(element.namespaceURI, namespace):
                self.extensions.append(element)
                continue

            elif localName == 'message':
                name = DOM.getAttr(element, 'name')
                docs = GetDocumentation(element)
                message = self.addMessage(name, docs)
                parts = DOM.getElements(element, 'part', NS_WSDL)
                message.load(parts)
                continue

    def _import(self, document, element):
        namespace = DOM.getAttr(element, 'namespace', default=None)
        location = DOM.getAttr(element, 'location', default=None)
        if namespace is None or location is None:
            raise WSDLError(
                'Invalid import element (missing namespace or location).'
                )

        # Sort-of support relative locations to simplify unit testing. The
        # WSDL specification actually doesn't allow relative URLs, so its
        # ok that this only works with urls relative to the initial document.
        location = urllib.basejoin(self.location, location)

        obimport = self.addImport(namespace, location)
        obimport._loaded = 1

        importdoc = DOM.loadFromURL(location)
        try:
            if location.find('#') > -1:
                idref = location.split('#')[-1]
                imported = DOM.getElementById(importdoc, idref)
            else:
                imported = importdoc.documentElement
            if imported is None:
                raise WSDLError(
                    'Import target element not found for: %s' % location
                    )

            imported_tns = DOM.getAttr(imported, 'targetNamespace')
            importer_tns = namespace

            if imported_tns != importer_tns:
                return

            if imported.localName == 'definitions':
                imported_nodes = imported.childNodes
            else:
                imported_nodes = [imported]
            parent = element.parentNode
            for node in imported_nodes:
                if node.nodeType != node.ELEMENT_NODE:
                    continue
                child = DOM.importNode(document, node, 1)
                parent.appendChild(child)
                child.setAttribute('targetNamespace', importer_tns)
                attrsNS = imported._attrsNS
                for attrkey in attrsNS.keys():
                    if attrkey[0] == DOM.NS_XMLNS:
                        attr = attrsNS[attrkey].cloneNode(1)
                        child.setAttributeNode(attr)
        finally:
            importdoc.unlink()


class Element:
    """Common base class for element representation classes."""
    def __init__(self, name=None, documentation=''):
        self.name = name
        self.documentation = documentation
        self.extensions = []

    def addExtension(self, item):
        self.extensions.append(item)


class SimpleTypeDefinition:
    """Represents an xml schema simple type definition."""

class ComplexTypeDefinition:
    """Represents an xml schema complex type definition."""

class AttributeDeclaration:
    """Represents an xml schema attribute declaration."""

class ElementDeclaration:
    """Represents an xml schema element declaration."""
    def __init__(self, name, type=None, targetNamespace=None):
        self.name = name

    targetNamespace = None
    annotation = None
    nillable = 0
    abstract = 0
    default = None
    fixed = None
    scope = 'global'
    type = None
    form = 0
    # Things we will not worry about for now.
    id_constraint_defs = None
    sub_group_exclude = None
    sub_group_affils = None
    disallowed_subs = None










class AttributeGroupDefinition:
    """Represents an xml schema attribute group definition."""

class IdentityConstraintDefinition:
    """Represents an xml schema identity constraint definition."""

class ModelGroupDefinition:
    """Represents an xml schema model group definition."""

class NotationDeclaration:
    """Represents an xml schema notation declaration."""

class Annotation:
    """Represents an xml schema annotation."""

class ModelGroup:
    """Represents an xml schema model group."""

class Particle:
    """Represents an xml schema particle."""

class WildCard:
    """Represents an xml schema wildcard."""

class AttributeUse:
    """Represents an xml schema attribute use."""


class ElementComponent:
    namespace = ''
    name = ''
    type = None
    form = 'qualified | unqualified'
    scope = 'global or complex def'
    constraint = ('value', 'default | fixed')
    nillable = 0
    id_constraint_defs = None
    sub_group_affil = None
    sub_group_exclusions = None
    disallowed_subs = 'substitution, extension, restriction'
    abstract = 0
    minOccurs = 1
    maxOccurs = 1
    ref = ''

class AttributeThing:
    name = ''
    namespace = ''
    typeName = ''
    typeUri = ''
    scope = 'global | local to complex def'
    constraint = ('value:default', 'value:fixed')
    use = 'optional | prohibited | required'

class ElementDataType:
    namespace = ''
    name = ''
    element_form = 'qualified | unqualified'
    attr_form = None
    type_name = ''
    type_uri = ''
    def __init__(self, name, namespace, type_name, type_uri):
        self.namespace = namespace
        self.name = name
        # type may be anonymous...
        self.type_name = type_name
        self.type_uri = type_uri

    def checkValue(self, value, context):
        # Delegate value checking to the type of the element.
        typeref = (self.type_uri, self.type_name)
        handler = context.serializer.getType(typeref)
        return handler.checkValue(value, context)

    def serialize(self, name, namespace, value, context, **kwargs):
        if context.check_values:
            self.checkValue(value, context)
        # Delegate serialization to the type of the element.
        typeref = (self.type_uri, self.type_name)
        handler = context.serializer.getType(typeref)
        return handler.serialize(self.name, self.namespace, value, context)

    def deserialize(self, element, context):
        if element_is_null(element, context):
            return None
        # Delegate deserialization to the type of the element.
        typeref = (self.type_uri, self.type_name)
        handler = context.serializer.getType(typeref)
        return handler.deserialize(element, context)



def parse_schema(data):
    targetNS = ''
    attributeFormDefault = 0
    elementFormDefault = 0
    blockDefault = ''
    finalDefault = ''
    language = None
    version = None
    id = ''
'''