Hi
I have just started to evaluate the XML Schema Model of Castor 0.9.9.
In the past I have implemented an XML schema processor using C++.
During that time I did a lot of reading in the XML schema recommendation.
Meanwhile, I'm looking for a schema model implemented in Java.
When looking more closely at the schema model created by the SchemaReader,
I found some results which look like inconsistencies with the XML schema spec.
If I did not miss something, they might deserve to be fixed
before the final release.
Before going into details:
(1) seems to be a severe bug in conjunction with schema composition
and namespace handling and there is no simple workaround
(2) seems to be a severe bug when using a hierarchy of complex types
with attributes
(3) deals with a very special and probably even exotic case
At least for fixing (1) some modifications in
org.exolab.castor.xml.schema.Schema
are required - maybe I could assist on that.
Best regards
Uli
(1) Namespace handling
===================
Various unqualified references to named global objects without a namespace
are not resolved correctly. This affects usage of the following attributes
which have a type QName as of the Schema for Schemas:
- ref (used in attribute, element, group, attributeGroup)
- type (used in attribute, element)
- base (used in restriction, extension)
- substitutionGroup (used in element)
- itemType (used in list)
So far, I have not tested all these scenarios, only the following
- <xs:element ref="...">
- <xs:attribute ref="...">
- <xs:attribute ... type="...">
- <xs:attributeGroup ref="...">
- <xs:group ref="...">
The following example illustrates the bug for <xs:attribute ref="...">:
withTNS.xsd
<xs:schema targetNamespace="NS1"
xmlns:xs="http://www.w3.org/2001/XMLSchema";>
<xs:import schemaLocation="./noTNS.xsd"/>
<xs:attribute name="A1" type="xs:date"/>
<xs:element name="E1">
<xs:complexType>
<xs:attribute ref="A1"/>
</xs:complexType>
</xs:element>
</xs:schema>
noTNS.xsd:
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema";>
<xs:attribute name="A1" type="xs:time"/>
</xs:schema>
As there is no namespace declaration for the default namespace in withTNS.xsd,
the QName value of the ref attribute in <xs:attribute ref="A1"/> is {-,A1},
i.e. without any URI. Hence, it should resolve to attribute A1 as declared in
noTNS.xsd. Unfortunately, when calling attrDecl.getReference() for the attrDecl
constructed from <xs:attribute ref="A1"/>, the global attribute declaration for
A1 in withTNS.xsd is returned.
When looking for a respective bug report I occasionally found a schema at
http://jira.codehaus.org/browse/CASTOR-1105 which is accepted by Castor, but
should not:
- references like type="string" are not valid if
(a) there is no default namespace declaration
xmlns="http://www.w3.org/2001/XMLSchema";
and
(b) there is no user-defined type named "string" being defined in a schema
without a targetNamespace
(2) Attribute Declarations and attribute wildcards inherited from base type
=======================================================================
Look at the following schema fragment:
<xs:complexType name="C1">
<xs:sequence>
<xs:element name="E1-C1" minOccurs="0" maxOccurs="27"/>
</xs:sequence>
<xs:attribute name="A1-C1" type="xs:float"/>
</xs:complexType>
<xs:complexType name="C2">
<xs:complexContent>
<xs:extension base="C1">
<xs:choice>
<xs:element name="E1-C2"/>
</xs:choice>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<xs:complexType name="C3">
<xs:complexContent>
<xs:restriction base="C1">
<xs:sequence>
<xs:element name="E1-C1" minOccurs="0" maxOccurs="1"/>
</xs:sequence>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
The following should show up in the schema model:
(a) Both derived complexTypes, C2 and C3 should have an attribute use with
name "A1-C1"
Castor does not return that!
See "3.4.2 XML Representation of Complex Type Definitions"
(http://www.w3.org/TR/xmlschema-1/#declare-type)
e.g. under "Complex Type Definition with simple content Schema Component"
you'll find
<cite>
{attribute uses}
A _union_ of sets of attribute uses as follows
...
3 if the type definition ·resolved· to by the ·actual value· of the
base [attribute] is a complex type definition, the {attribute uses}
of that type definition, unless the <restriction> alternative is
chosen,
in which case some members of that type definition's {attribute uses}
may not be included, ...
</cite>
In a similar way, an attribute wildcard is propagated to the properties
of the derived type.
(b) C2 should have an _effective_ content model which is a sequence
containing two particles:
- the first one is the sequence as defined in "C1",
- the second is the choice as defined in "C2"
"Complex Type Definition with complex content Schema Component"
(3) Restricting an complexType with complexContent to complexType with
simpleContent
================================================================================
- see "Schema Component Constraint: Derivation Valid (Restriction, Complex)"
(http://www.w3.org/TR/xmlschema-1/#derivation-ok-restriction)
5.2.2.2 The {content type} of the {base type definition} must be
elementOnly
or mixed and have a particle which is ·emptiable· as defined in
Particle Emptiable (§3.9.6).
The following schema meets these constraints:
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema";>
<xs:complexType name="CT1" mixed="true">
<xs:sequence>
<xs:element name="E1-CT1" minOccurs="0" maxOccurs="1"/>
</xs:sequence>
</xs:complexType>
<xs:complexType name="CT2">
<xs:simpleContent>
<xs:restriction base="CT1">
<xs:simpleType>
<xs:restriction base="xs:int"/>
</xs:simpleType>
</xs:restriction>
</xs:simpleContent>
</xs:complexType>
</xs:schema>
but is rejected by Castor with the following exception:
complexType: CT2In a simpleContent when using restriction the base type must be
a complexType whose base is a simpleType.
at
org.exolab.castor.xml.schema.reader.ComponentReader.error(ComponentReader.java:213)
at
org.exolab.castor.xml.schema.reader.SchemaUnmarshaller.startElement(SchemaUnmarshaller.java:470)
at
org.exolab.castor.xml.schema.reader.Sax2ComponentReader.startElement(Sax2ComponentReader.java:253)
at org.apache.xerces.parsers.AbstractSAXParser.startElement(Unknown
Source)
at
org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanStartElement(Unknown
Source)
at
org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(Unknown
Source)
at
org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown
Source)
...
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