We have seen some schemas where the definition of a namespace is split between several schemas, each defining a subset of the namespace. An example of what I mean is attached:
schemaA.xsd defines namespaceA, and imports both schemaB.xsd and schemaC.xsd into namespaceB. It then defines an element of each of the types defined in schemas B and C, in namespaceB. This generates errors on validation. It appears that xerces ignores the second import, so the type defined in schemaC.xsd is not available when it is used to define the element. XMLspy, however accepts this use, and validates the instance fine. Also, the IBM XML Schema quality checker[3], claims there is no error in schemaA.xsd. As schemas and namespaces get larger, and more complicated, I expect this sort of separation to become more and more widespread. I think that where we are having trouble, is with the following extract from [1]: Given that the schemaLocation [attribute] is only a hint, it is open to applications to ignore all but the first <import> for a given namespace, regardless of the �actual value� of schemaLocation, but such a strategy risks missing useful information when new schemaLocations are offered. Ignoring the second one seems to be allowed. It is also stated to be implementation dependent in [2], however I believe that supporting this use case is something we should do. That said, it could prove difficuult to stop ignoring subsequent imports for a namespace, as it opens up the problem of duplicate imports, and circular imports. Should I bug report this, or does it need discussing first? David [1] http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/#element-import [2] http://lists.w3.org/Archives/Public/www-xml-schema-comments/2000OctDec/0480.html [3] http://www.alphaworks.ibm.com/tech/xmlsqc -- David Sheldon, Client Services DecisionSoft Ltd. Telephone: +44-1865-203192 http://www.decisionsoft.com
<Top xmlns="http://www.example.com/namespaceA"; xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xsi:noNamespaceSchemaLocation='schemaA.xsd'> <B>12345</B> <C>AAAAA</C> </Top>
<?xml version="1.0" encoding="UTF-8" ?> <xsd:schema elementFormDefault='qualified' attributeFormDefault='unqualified' targetNamespace='http://www.example.com/namespaceA' xmlns='http://www.example.com/namespaceA' xmlns:xsd='http://www.w3.org/2001/XMLSchema' xmlns:nsB='http://www.example.com/namespaceB'> <xsd:import namespace='http://www.example.com/namespaceB' schemaLocation='schemaB.xsd' /> <xsd:import namespace='http://www.example.com/namespaceB' schemaLocation='schemaC.xsd' /> <xsd:element name='Top'> <xsd:complexType> <xsd:sequence> <xsd:element name='B' type='nsB:TypeB' /> <xsd:element name='C' type='nsB:TypeC' /> </xsd:sequence> </xsd:complexType> </xsd:element> </xsd:schema>
<?xml version="1.0" encoding="UTF-8" ?> <xsd:schema elementFormDefault='qualified' attributeFormDefault='unqualified' targetNamespace='http://www.example.com/namespaceB' xmlns='http://www.example.com/namespaceB' xmlns:xsd='http://www.w3.org/2001/XMLSchema'> <xsd:simpleType name='TypeB'> <xsd:restriction base='xsd:string'> <xsd:pattern value='[0-9]{5}' /> </xsd:restriction> </xsd:simpleType> </xsd:schema>
<?xml version="1.0" encoding="UTF-8" ?> <xsd:schema elementFormDefault='qualified' attributeFormDefault='unqualified' targetNamespace='http://www.example.com/namespaceB' xmlns='http://www.example.com/namespaceB' xmlns:xsd='http://www.w3.org/2001/XMLSchema'> <xsd:simpleType name='TypeC'> <xsd:restriction base='xsd:string'> <xsd:pattern value='A{5}' /> </xsd:restriction> </xsd:simpleType> </xsd:schema>
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