This page is a subpage of CMDI 1.2

Generic attributes to CMDI namespace

The issue

All attributes in CMDI 1.1 instances are in no-namespace, this counts for both attributes defined in the component/profile specification and the CMDI common attributes (@ref and @componentId) which have special semantics. Currently, the Component Registry and schematron rules check for the presence of attributes with these names and rejects them. A better solution would be to allow any name for custom attributes and move the reserved attributes into a dedicated namespace.

Proposed solution

Leave custom attributes without namespace and put the following attributes in the same namespace as the elements, namely http://www.clarin.eu/cmd/ (an obvious namespace prefix would be cmd):

• ref
• componentId

Implementation examples

CMDI instance:

<CMD CMDVersion="1.2" 
  xsi:schemaLocation="http://www.clarin.eu/cmd/ http://www.clarin.eu/cmd/example/example-md-schema.xsd"  
  xmlns="http://www.clarin.eu/cmd/" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:cmd="http://www.clarin.eu/cmd/">
...
  <MyComponent myAttribute="value" cmd:ref="resourceProxy1" cmd:componentId="clarin.eu:cr1:c_1328259700912">...</MyComponent>

To achieve this we have to make the following changes to the XSD generated by comp2schema.xsl:

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:dcr="http://www.isocat.org/ns/dcr" xmlns:cmd="http://www.clarin.eu/cmd/" targetNamespace="http://www.clarin.eu/cmd/" elementFormDefault="qualified">         
    ...
    <!-- globally declare @ref and @ComponentId, so they have to be qualified -->
    <xs:attribute name="ref" type="xs:IDREFS"/>
    <xs:attribute name="ComponentId" type="xs:anyURI"/>
    ...
    <xs:element name="myComponent" ... >
        <xs:complexType>
            <xs:sequence>
                ...
            </xs:sequence>
            <!-- refer to the globally declared attributes -->
            <xs:attribute ref="cmd:ref"/>
            <xs:attribute ref="cmd:ComponentId" fixed="clarin.eu:cr1:c_1328259700912"/>
        </xs:complexType>
    </xs:element>
    ...
</xs:schema>         

Note: cleanup-xsd.xsl also needs to be adopted as it currently will prune away the new global <xs:attribute/> elements.

Tickets

Tickets in the CMDI 1.2 milestone with the keyword attributenamespace:

Ticket	Summary	Owner	Component	Priority	Status
#236	Namespace prefixes for generic CMDI attributes (and possibly elements)	Dieter Van Uytvanck	ComponentSchema	major	closed

Discussion

Discuss the topic in general below this point