Proposed Part 1 Text for REQUIRED Extension Properties

I propose the following addition to Part 1 to clarify the meaning of 
REQUIRED extension properties:

6.4 Validity of Extended Component Model Instances

As stated above, WSDL 2.0 provides a component model extensibility 
mechanism which allows new properties and components to be specified. An 
extension specification may also add new constraints or modify existing 
ones. The validity of a component model instance is therefore dependent on 
the set of extension specifications that it is asserted to conform to. An 
extended component model is the component model as defined by the WSDL 2.0 
Core Language specification together with a set of extension 
specifications. A component model instance is valid with respect to an 
extended component model if it conforms to the core language and the given 
set of extension specifications, with the provision that any extension 
specification may explicitly override a constraint in another 
specification.

6.4.1 Semantics of REQUIRED Properties in Extended Component Models

When an extension specification defines a property to be REQUIRED, this is 
to be understood that the property is only REQUIRED within the context an 
extended component model that includes the extension specification. An 
extension specification may also define co-occurence constraints that 
further qualify the conditions under which the property is REQUIRED. Note 
that an extension specification may override the REQUIRED constraint on 
any property defined in another specification and make it OPTIONAL.  Thus, 
a property is only REQUIRED when the following conditions hold:

the extension specification is in the extended component model
all co-occurence constraints, if any, in the extension specification are 
satisified
no other extension specification in the extension component model 
overrides this constraint

Arthur Ryman,
IBM Software Group, Rational Division

blog: http://ryman.eclipsedevelopersjournal.com/
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