Import/Include - a proposal

Import/Include in WS-CDL

Proposal:

Given that the XInclude mechanism [ref] has been created for the  
express purpose of providing a generic mechanism for recognizing and  
processing inclusions in XML grammars I propose that we use it as the  
basis for our own importation mechanism in WS-CDL. This mechanism would  
be a syntactic inclusion identical to XInclude and would conform to the  
processing model of XInclude. Parsing and validation of a merged  
info-set (the result of XInclusion) would then be a separate and  
orthogonal process.

This would allow us to close the following issues:
	Issue 469 - because it does a merge on info-sets and the correctness  
of the result is WS-CDL's problem.
	Issue 484 - because XInclude doesn't care I would suggest neither  
should we.
	Issue 485 - doesn't overide at all and in cases with clashes it could  
be a schema error.
	Issue 561 - see 485 above
	Issue 609 - not so sure on this one but my sense is that it is  
irrelevant to a syntactic inclusion mechanism and so can be closed
	Issue 611: XInclude handles this (see processing model and uri  
resolution).

For summary of above issues see  
(http://lists.w3.org/Archives/Public/public-ws-chor/2004Jul/att-0015/ 
draft-import-mm2-062904.pdf)




Excerpts below are taken from http://www.w3.org/TR/xinclude/


1.2 Relationship to XML External Entities
... XInclude operates on information sets and thus is orthogonal to  
parsing....

1.3 Relationship to DTDs

XInclude defines no relationship to DTD validation. XInclude describes  
an infoset-to-infoset transformation and not a change in XML 1.0  
parsing behavior. XInclude does not define a mechanism for DTD  
validation of the resulting infoset.

1.4 Relationship to XML Schemas

XInclude defines no relationship to the augmented infosets produced by  
applying an XML schema. Such an augmented infoset can be supplied as  
the input infoset, or such augmentation might be applied to the infoset  
resulting from the inclusion.

1.5 Relationship to Grammar-Specific Inclusions

Special-purpose inclusion mechanisms have been introduced into specific  
XML grammars. XInclude provides a generic mechanism for recognizing and  
processing inclusions, and as such can offer a simpler overall  
authoring experience, greater performance, and less code redundancy.


4 Processing Model

Inclusion as defined in this document is a specific type of [XML  
Information Set] transformation.

[Definition: The input for the inclusion transformation consists of a  
source infoset.] [Definition: The output, called the result infoset, is  
a new infoset which merges the source infoset with the infosets of  
resources identified by IRI references appearing in xi:include  
elements.] Thus a mechanism to resolve URIs and return the identified  
resources as infosets is assumed. Well-formed XML entities that do not  
have defined infosets (e.g. an external entity with multiple top-level  
elements) are outside the scope of this specification, either for use  
as a source infoset or the result infoset.

xi:include elements in the source infoset serve as inclusion  
transformation instructions. [Definition: The information items located  
by the xi:include element are called the top-level included items].  
[Definition: The top-level included items together with their  
attributes, namespaces, and descendants, are called the included  
items]. The result infoset is essentially a copy of the source infoset,  
with each xi:include element and its descendants replaced by its  
corresponding included items.