[NEW ISSUE] SCA Assembly XSD extensibility is broken if new implementationor binding types are added from other namespaces than the SCA one

[Raymond Feng <rfeng@us.ibm.com>]

Target: http://tools.oasis-open.org/version-control/browse/wsvn/sca-assembly/SCA_XSDS/sca-core-1.1-cd04.xsd

Description:

The Component is defined in sca-core-1.1-cd04.xsd
as follows:
<complexType name="Component">
      <complexContent>
         <extension
base="sca:CommonExtensionBase">
           
<sequence>
       
       <element ref="sca:implementation"
minOccurs="0"/>
           
   <choice minOccurs="0" maxOccurs="unbounded">
           
      <element name="service" type="sca:ComponentService"/>
           
      <element name="reference" type="sca:ComponentReference"/>
           
      <element name="property" type="sca:PropertyValue"/>
           
   </choice>
       
       <any namespace="##other" processContents="lax"
minOccurs="0" 
       
            maxOccurs="unbounded"/>
           
</sequence>
           
<attribute name="name" type="NCName" use="required"/>
           
<attribute name="autowire" type="boolean" use="optional"/>
           
<attribute name="constrainingType" type="QName"
use="optional"/>
           
<attribute name="requires" type="sca:listOfQNames"

           
           use="optional"/>
           
<attribute name="policySets" type="sca:listOfQNames"

           
           use="optional"/>
         </extension>
      </complexContent>
   </complexType>

Let's assume that we extend base SCA
by adding a new implementation type: {http://example.com}implementation.xyz.
The XSD (xyz.xsd) for implementation.xyz is illustrated below.

<schema xmlns="http://www.w3.org/2001/XMLSchema"
    targetNamespace="http://example.com"
    xmlns:sca="http://docs.oasis-open.org/ns/opencsa/sca/200903"
    xmlns:t="http://example.com"
..>
  <import namespace="http://docs.oasis-open.org/ns/opencsa/sca/200903"
schemaLocation="sca-1.1-cd04.xsd"/>
  <element name="implementation.xyz"
type="t:XYZImplementation" substitutionGroup="sca:implementation"/>

    <complexType name="XYZImplementation">
        <complexContent>
           
<extension base="sca:Implementation">
           
    <sequence>
           
        ...
           
    </sequence>
        ...
           
</extension>
        </complexContent>
    </complexType>

</schema>

Run XML schema validation in Eclipse
reports that {http://docs.oasis-open.org/ns/opencsa/sca/200903}implementation
and WC {http://docs.oasis-open.org/ns/opencsa/sca/200903}##other
create the ambiguity. This issue can be further explained using the following
composite files.

Now we define an SCA composite (version
1):

<composite xmlns="http://docs.oasis-open.org/ns/opencsa/sca/200903"
    xmlns:t="http://example.com"
    targetNamespace="http://test"
    name="MyComposite">

    <component name="MyComponent">
       
<t:implementation.xyz .../> <!-- The schema cannot tell if this
is ##other or an substitutionGroup of sca:implementation -->
    </component>
</composite>

The composite file exposes the ambiguity
as the <t:implementation.xyz> can be interpreted as <sca:implemention>
or <any namespace="##other">. 

If we remove @substitutionGroup from
implementation.xyz as a workaround, the following composite (version 2)
fails the schema validation.

<composite xmlns="http://docs.oasis-open.org/ns/opencsa/sca/200903"
    xmlns:t="http://example.com"
    targetNamespace="http://test"
    name="MyComposite">

    <component name="MyComponent">
       
<t:implementation.xyz .../> <!-- The schema expects an substitutionGroup
of sca:implementation -->
        <service
name="MyService">
           
<binding.ws uri="http://localhost:8086/MyService"/>
        </service>
    </component>
</composite>

The similar issue applies to bindings
too if a binding is defined in a different namespace other than the SCA
one.

Proposal:

None (It doesn't seem to be a simple
way to fix it :-(

Thanks,
Raymond

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Raymond Feng
Senior Software Engineer, Apache Tuscany PMC Member & Committer 
IBM Bay Area Lab, 1001 E Hillsdale Blvd, Suite 400,
Foster City, CA 94404, USA
E-mail: rfeng@us.ibm.com,
Notes: Raymond Feng/Burlingame/IBM, Tel: 650-645-8117,
T/L: 367-8117
Apache Tuscany: http://tuscany.apache.org

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