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Re: LC-185 comments from XML Core WG

From: Paul Grosso <pgrosso@arbortext.com>
Date: Sun, 08 Oct 2000 12:00:30 -0400
Message-Id: <3.0.32.20001008115959.00fe6f14@pophost.arbortext.com>
To: "C. M. Sperberg-McQueen" <cmsmcq@acm.org>
Cc: w3c-xml-core-wg@w3.org, W3C XML Schema Comments list <www-xml-schema-comments@w3.org>
At 22:56 2000 10 05 -0600, C. M. Sperberg-McQueen wrote:
>You raised the point registered as issue LC-185, which suggests that
>attention probably needs to be paid to the provision of
>schema-specific information in the post-schema-validation infoset.
>
>We thank you for the observation, and we agree.  After considering a
>variety of alternatives, the WG eventually decided to expose the
>schema information in the form of information items corresponding to
>the 'components' described in the XML Schema specification, each
>information item having the properties ascribed in the spec to the
>component.  We believe that exposing the schema in this way is the
>best method of avoiding the complications which would otherwise result
>from inclusion and import of other schema documents, etc.

It is not clear to me whether the creation of the PSV is seen as a process
that augments the existing infoset or as a process of creating a completely
new infoset.  

I'm not sure what a 'component' is, but I gather that the PSV infoset
is expected to augment the pre-SV infoset with (schema-specific) infoitems
each with various properties.  Depending on just how this is done, this 
might mean that things that were children of a given infoitem might become
grandchildren.  In the least, it appears to imply that infoitems that had 
a "next/previous sibling" relationship would now have another infoitem in 
between.  Such changes to the structure of the tree must be considered in
light of XPath like addressing into the infoset.

If the PSV creation is more of an "augmentation" and things like XPointer, 
XSLT, or anything else that uses XPath or a DOM API or some similar tree-based 
notation to address into the original document's infoset are expected to 
continue to work unaltered on the PSV infoset, then the addition of infoitems
throughout the tree (as opposed to just new properties on existing infoitems
[which properties could perhaps be "references" to one or more infoitems]
or addition of infoitems "outside" the tree [e.g., in the infoset but not
descendants of the document's root element]) will require new "axes" 
(to use the XPath terminology) to allow access to the new infoitems while 
allowing existing addresses to continue to work.  

If PSV creation is seen as the creation of a new infoset, then it must 
be realized that XPointers and such designed to point into the original 
document's infoset will not work with the PSV infoset, and either the
inability to use XPointers (and XSLT and such) with PSV infosets must be 
determined to be acceptable or there needs to be some process defined
in parallel to PSV creation that describes how to modify existing addresses
into the pre-SV to become appropriate addresses into the PSV.

Has the XML Schema work addressed these issues?

paul
Received on Sunday, 8 October 2000 12:00:27 GMT

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