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Subject: Re: [sca-bpel] Component Types in SCA


I sympathise - it does get confusing.

I tried before now to get the name of "component type" changed to "implementation info".  Names mean a lot, since
they give people impressions of what they mean.

The real meaning of "component type" is really that it is a description of the actual configurable aspects of an
implementation (that is why "implementation info" would be more appropriate).

The component in a composite is a configuration of some implementation - strictly, the component does not have
a "type" - it is configuring a type.  Further to confuse things, it is not necessary for a component to configure all of
the configurable aspects of an implementation (eg the implementation may have a configurable property, but if
the property has a default value, then a using component can leave this untouched).

For the composite to FORCE the component type of the implementation, the concept of "constraining type" was
introduced, to help in the case of top-down design where there is a desire for the composite to dictate the "shape"
of the implementation that it will (later) use. This is the equivalent of the "component defining the type of the
component" - but in reality it is defining the type of the implementation (or at least its SCA-configurable form)

I hope this helps dispel some of the darkness.

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

"Najeeb Andrabi" <nandrabi@tibco.com>

12/02/2008 20:11

[sca-bpel] Component Types in SCA

       I would like to make a comment about Component Types in SCA. This is in context with defining a component type file for BPEL implementations. I am curious about the fact that a component cannot refer a component type: it has to infer what its type might be using implementation.* element. I don’t understand the rationale behind this approach. Component type defines the type of component so why it cannot refer it. Approach of referring ones type is used everywhere in specifications like XML schema, WSDL, BPEL etc. e.g. a schema element can have a reference to complex type that defines the type of the element.
      My comment may be because of lack of understanding of SCA assembly specification. But, from my understanding of the specification I think we should allow components to refer their type.

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