Further Thoughts on Issue 87

[ashok malhotra <ashok.malhotra@oracle.com>]

Issue 87 was raised because the XPath syntax in the example Snippet 3-5 
in section 3.4 was thought to be
incorrect.  On subsequent checking it turned out that the syntax was, 
indeed, correct.
An XPath expression that consists of an unadorned element name selects 
all element children of the
context node with that name.

The spec (lines 457-458) says "Note that the XPath expression will 
always be evaluated within the context of an attachment considering 
elements where binding instances or implementations are allowed to be 
present. The expression is evaluated against /the parent element of any 
binding or implementation element/."

Thus, if a policySet is attached high at the component level, its 
applicability needs to be examined against the parent element
of any binding or implementation element.  That is, the context node is 
set, in turn to each such parent element and the XPath is then 
evaluated.  This seems unduly onerous, so I suggested changing the spec 
to say that the context node
is the root of the SCDL document.  An expression such as //binding.ws 
would then select all binding.ws elements anywhere
in the SCDL.  This seems to me to be significantly simpler to evaluate.

Dave, pointed out that this would not cover included composites and that 
this was a problem.

On further reflection, I realized that to evaluate the @attachTp in the 
case of external attachment we create an
*/Infoset for External Attachment/*  See line 844.  This does cover the 
included composites and the @appliesTo in
policySets could be evaluated using the root of this constructed InfoSet 
as the context element.

What do people think?  Details of the construction of the */Infoset for 
External Attachment/* are copied below for
easy reference.

1.       The Domain is treated as a special composite, with a blank name 
- ""

2.       Where one composite includes one or more other composites, it 
is the including composite which is addressed by the XPath and its 
contents are the result of preprocessing all of the include elements

    --Where the policySet is intended to be specific to a particular use 
of a composite file (rather than to all uses of the   composite), the 
structuralURI of a component is used to attach policySet to a specific 
use of a nested component, as described in the SCA Assembly 
specification [SCA-Assembly].

    --The XPath expression can make use of the unique URI to indicate 
specific use instances, where different policySets need to be used for 
those different instances.

-- 
All the best, Ashok