Re: [sca-assembly] Question for Debate concerning Component @nameattribute

[Anish Karmarkar <Anish.Karmarkar@oracle.com>]

 > I note that the @name attribute is declared as an NCName, which
 > implies
 > that it is the local part of a QName, with
 > the namespace being taken from the @targetNamespace of the enclosing
 > <composite/> element.

I never took that as the implication.
Composites are identified by QNames and now we have structural URIs to 
identify components. xs:NCName is just a restricted form of xs:string. 
NCName does not necessarily mean that it is local part of some QName 
definition. NCName does not allow things like white space characters, 
':' etc that string allows. Given the syntax of the structural URI of a 
component, I like the restrictions that NCName imposes on @name of the 
component element. A string or anyURI would make the structural URI of a 
component look really strange.

-Anish
--

Mike Edwards wrote:
> 
> Folks,
> 
> It has come to my attention that there may be an inconsistency in the 
> way that Component @name attributes are declared and
> used by SCA Assembly.
> 
> If we look at the definition of the <component/> element, we find:
> 
>     <complexType name="Component">
> 
>         <sequence>
> 
>              <element ref="sca:implementation" minOccurs="0" 
> maxOccurs="1"/>
> 
>              <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"/>
> 
>         <anyAttribute namespace="##other" processContents="lax"/>
> 
>     </complexType>
> 
> 
> I note that the @name attribute is declared as an NCName, which implies 
> that it is the local part of a QName, with
> the namespace being taken from the @targetNamespace of the enclosing 
> <composite/> element.
> 
> However, I also note that EVERY use that we have defined for this @name 
> attribute actually treats the component
> @name as a relative URI (or part of a relative URI).
> 
> Component names are used:
> 
> - as targets for wires and references (or as part of them eg. 
> "component1/service1")
> - as sources for wires
> - as promoted elements (for composite services and composite references)
> - in structuralURIs, for identifying specific usage instances of a 
> nested component
> 
> If we REALLY had them as QNames, then surely the namespace would have to 
> become part of these usages?
> But wouldn't that make them very cumbersome?  Every time we mention a 
> component name it has to be
> qualified with the namespace?
> 
> This gets interesting once we look at the <include/> functionality.  In 
> principle, an included composite could have
> its own namespace.  It might have its own unique namespace as a 
> technique for ensuring lack of @name clashes
> when its contents are included by some other composite - we have a 
> requirement that all Component @names
> are unique within a composite.  But now we have to use that namespace 
> whenever the including composite wants
> to refer to some component from the included one - and if there are 
> nested includes, heaven help us.
> 
> 
> 
> I think that we should consider marking the @name attribute of a 
> Component as either a string or as a URI.  Make it
> clear that it is not a QName and is not affected by the namespace of the 
> containing <composite/>.  This leaves
> the burden of ensuring uniqueness, but stylised names (eg based on using 
> the composite name as a stem)
> can achieve this with little real burden.
> 
> 
> 
> Yours,  Mike.
> 
> Strategist - Emerging Technologies, SCA & SDO.
> Co Chair OASIS SCA Assembly TC.
> IBM Hursley Park, Mail Point 146, Winchester, SO21 2JN, Great Britain.
> Phone & FAX: +44-1962-818014    Mobile: +44-7802-467431  
> Email:  mike_edwards@uk.ibm.com
> 
> 
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