DCMI XML Schemas

The schemas

Base schemas Schema: dc.xsd Target XML Namespace: http://purl.org/dc/elements/1.1/ Schema: dcterms.xsd Target XML Namespace: http://purl.org/dc/terms/ Schema: dcmitype.xsd Target XML Namespace: http://purl.org/dc/dcmitype/

Container schemas Schema: simpledc.xsd Target XML Namespace: none Schema: qualifieddc.xsd Target XML Namespace: none

Sample application schemas Schema: appsimpledc.xsd Target XML Namespace: [decided by application] Schema: appqualifieddc.xsd Target XML Namespace: [decided by application]

2. The parsers/validators

• XSV 2.2-1 of 2002/12/01 21:59:33
• Xerces Xerces-J 2.2.1 2002/11/11 17:40
• MSXML4 Microsoft XML Core Services 4.0 SP1

Results

testsimpledc.xml
Parser	Result	Messages
XSV	Schema and instance accepted as valid
Xerces	Schema and instance accepted as valid
MSXML4	Schema and instance accepted as valid
testqualifieddc.xml
XSV	Schema and instance accepted as valid
Xerces	Schema dcterms.xsd rejected as invalid	[Error] dcterms.xsd:nnn:nn: src-ct.2: Complex Type Definition Representation Error for type 'xxxx'. When simpleContent is used, the base type must be a complexType whose content type is simple, or, only if extension is specified, a simple type. (where 'xxxx' is the name of a complexType corresponding to one of the encoding schemes.)
MSXML4	Schema and instance accepted as valid

The "dc:SimpleLiteral" problem

The schema dc.xsd defines a base complexType called SimpleLiteral:

  <xs:complexType name="SimpleLiteral">
   <xs:complexContent mixed="true">
    <xs:restriction base="xs:anyType">
     <xs:sequence>
      <xs:any processContents="lax" minOccurs="0" maxOccurs="0"/>
     </xs:sequence>
     <xs:attribute ref="xml:lang" use="optional"/>
    </xs:restriction>
   </xs:complexContent>
  </xs:complexType>
    

Encoding schemes are represented as complexTypes derived from the SimpleLiteral complexType. For example, the complexType corresponding to the encoding scheme for "W3CDTF" is as follows:

  <xs:complexType name="W3CDTF">
   <xs:simpleContent>
    <xs:restriction base="dc:SimpleLiteral">
        <xs:simpleType>
           <xs:union memberTypes="xs:gYear xs:gYearMonth xs:date xs:dateTime"/>
        </xs:simpleType>
        <xs:attribute ref="xml:lang" use="prohibited"/>
    </xs:restriction>
   </xs:simpleContent>
  </xs:complexType>
  

This derivation of a complexType with simpleContent by restriction of a base complexType with complexContent is valid under section 3.4.6 of XML Schema Part 1: Structures, specifically item 5.1.2 of the section "Schema Component Constraint: Derivation Valid (Restriction, Complex)", because the base complexContent is mixed and emptiable.

This was confirmed by Henry Thompson, see e.g.
http://www.w3.org/2001/05/xmlschema-rec-comments#pfiSimpleContent
http://lists.w3.org/Archives/Public/xmlschema-dev/2002Oct/0005.html
http://lists.w3.org/Archives/Public/xmlschema-dev/2002Oct/0008.html

Conclusion: Xerces appears to be behaving incorrectly in rejecting this derivation.