Xs:group refs and "ORA-30936: Maximum number (1) of XML nodes exceeded'

Question

We registered a subset of the IBM DITA schemas in Oracle XDB. These schemas contain a lot of xs:group definitions where references to these groups contain "minOccurs" and "maxOccurs" atttributes, for instance:
<xs:group name="category">
<xs:sequence>
<xs:element ref="category"/>
</xs:sequence>
</xs:group>
<xs:complexType name="metadata.class">
<xs:sequence>
<xs:group ref="audience" minOccurs="0" maxOccurs="unbounded"/>
<xs:group ref="category" minOccurs="0" maxOccurs="unbounded"/>
<xs:group ref="keywords" minOccurs="0" maxOccurs="unbounded"/>
<xs:group ref="prodinfo" minOccurs="0" maxOccurs="unbounded"/>
<xs:group ref="othermeta" minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="mapkeyref" type="xs:string"/>
<xs:attributeGroup ref="global-atts"/>
<xs:attribute ref="class" default="- topic/metadata "/>
</xs:complexType>
When we create an instance document that contains more than one "category" element under the element "metadata" element, like:
<metadata>
<audience type="purchaser" othertype="" job="using" otherjob="" experiencelevel="general"/>
<category/>
<category/>
</metadata>
we get the error: ORA-30936: Maximum number (1) of 'category' XML node elements exceeded
This error is not consistent with the schema and XML parsers like Xerces and the Oracle "XDK parser" think the instance is fine.
When we skip the reference to the group and reference the element definition "category" directly the problem is gone:
<xs:complexType name="metadata.class">
<xs:sequence>
<xs:group ref="audience" minOccurs="0" maxOccurs="unbounded"/>
<xs:element ref="category" minOccurs="0" maxOccurs="unbounded"/>
<xs:group ref="keywords" minOccurs="0" maxOccurs="unbounded"/>
<xs:group ref="prodinfo" minOccurs="0" maxOccurs="unbounded"/>
<xs:group ref="othermeta" minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="mapkeyref" type="xs:string"/>
<xs:attributeGroup ref="global-atts"/>
<xs:attribute ref="class" default="- topic/metadata "/>
</xs:complexType>
In this case the problems for the other group references like "audience" remain.
It looks like Oracle XDB doesn't honor the cardinality attributes "minOccurs" and "maxOccurs" on xs:group elements that are references. Does anyone experienced similar problems?
Thanks,
Maarten

Answer 1

This sounds like bug 5204107. You'll need to open a tar with Oracle Support if you need a fix for this..
It happens when a group is used once without a maxOccurs and then later with a maxOccurs.
The workaround is 'in-line' the group before registering the XML Schema. This can be done as follows (assuming the group definition and reference are in the same XML Schema)..
procedure expandGroup(xmlschema in out xmltype, groupName varchar2,xsdDirectory varchar2)
is
  xsdSchemaPath varchar2(512);
  groupModel xmltype;
  sequenceModel xmlType := xmlType('<xsd:sequence ' || xdb_namespaces.XMLSCHEMA_PREFIX_XSD || '><xsd:sequence/></xsd:sequence>');
  maxOccursValue binary_integer;
begin
  -- FInd the Group Definition
  if xmlSchema.existsNode('/xsd:schema//xsd:group[@ref="' || groupName || '"]',NAMESPACES) = 1 then
    if xmlSchema.existsNode('/xsd:schema/xsd:group[@name="' || groupName || '"]',NAMESPACES) = 1 then
      select extract
               xmlSchema,
               '/xsd:schema/xsd:group[@name="' || groupName || '"]',
               NAMESPACES
        into groupModel
        from dual; 
    else
      dbms_output.put_line('xsdDirectory = ' || xsdDirectory);
      select PATH,
             extract
               CONTENTS,
               '/xsd:schema/xsd:group[@name="' || groupName || '"]',
               NAMESPACES
        into xsdSchemaPath, groupModel
        from (
               select PATH, xdburitype(path).getXML() CONTENTS
                 from PATH_VIEW
                where under_path(res,xsdDirectory) = 1
       where existsNode
               CONTENTS,
               '/xsd:schema/xsd:group[@name="' || groupName || '"]',
               NAMESPACES
             ) = 1;
       dbms_output.put_line('Resolved ' || groupModel.extract('/xsd:group/@name',NAMESPACES).getStringVal() || ' in Schema ' || xsdSchemaPath);
    end if;
    if groupModel.existsNode('/xsd:group/xsd:annotation',NAMESPACES) = 1 then
      select deleteXML
               groupModel,
               '/xsd:group/xsd:annotation',
               NAMESPACES
        into groupModel
        from dual;
    end if;
    -- create a sequence that can be placed in-line in the XML Schema to replace the <group ref=""/>
    groupModel := groupModel.extract('/xsd:group/*',NAMESPACES);
    select updateXML
             sequenceModel,
             '/xsd:sequence/xsd:sequence',
            groupModel,
             NAMESPACES
      into sequenceModel
      from dual;
    if xmlSchema.existsNode('/xsd:schema//xsd:group[@ref="' || groupName || '" and not(@maxOccurs)]',NAMESPACES) = 1 then
      select updateXML
               xmlSchema,
               '/xsd:schema//xsd:group[@ref="' || groupName || '" and not(@maxOccurs)]',
              sequenceModel,
               NAMESPACES
        into xmlSchema
        from dual;
    end if;
    select insertChildXML
             sequenceModel,
             '/xsd:sequence',
             '@maxOccurs',
             'unbounded',
             NAMESPACES
      into sequenceModel
      from dual;
    if xmlSchema.existsNode('/xsd:schema//xsd:group[@ref="' || groupName || '" and @maxOccurs="unbounded"]',NAMESPACES) = 1 then
      select updateXML
               xmlSchema,
               '/xsd:schema//xsd:group[@ref="' || groupName || '" and @maxOccurs="unbounded"]',
               sequenceModel,
               NAMESPACES
        into xmlSchema
        from dual;
    end if;
    while xmlschema.existsNode('/xsd:schema//xsd:group[@ref="' || groupName || '"]',NAMESPACES) = 1 loop
      maxOccursValue := xmlSchema.extract('/xsd:schema//xsd:group[@ref="' || groupName || '"]/@maxOccurs').getNumberVal();
      select updateXML
               sequenceModel,
              '/xsd:sequence/@maxOccurs',
               maxOccursValue,
               NAMESPACES
        into sequenceModel
        from dual;
      select updateXML
               xmlSchema,
               '/xsd:schema//xsd:group[@ref="' || groupName || '" and @maxOccurs="' || maxOccursValue || '"]',
               sequenceModel,
               NAMESPACES
        into xmlSchema
        from dual;
    end loop;
  end if;
end;
--