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Two comments on the XML Query Data Model.

From: Murali Mani <mani@CS.UCLA.EDU>
Date: Thu, 28 Sep 2000 13:20:44 -0700 (PDT)
To: www-xml-query-comments@w3.org
Message-ID: <Pine.SOL.4.10.10009281302470.29577-100000@panther.cs.ucla.edu>

Hi,

I was reading the XML Query Data Model draft, and I had two possible
comments/questions. I would appreciate i could get the opinions of the
Query WG members on these.

Thanks - Murali.

===================

1. I believe one of the parallels to a relational table definition and
multiple rows in the table in the XML world is define one schema and have
multiple documents for it. From my glancing at the data model draft, I
could not find any mention of such a requirement. Is it not suitable to
define an XML repository/database as <schema, setOfDocs> pairs?

2. The Query WG relies on obtaining an ordered list of trees (also called
hedge, sometimes also called forest) for the result of a Path expression.
This is not provided by XPath which, I believe, defines a node set (one
of the four possible results of an XPath Expression) as an unordered set
of trees. Does not this additional requirement for the Query purposes
require more definitions in the data model? What I think is required is
that you define an order for nodes that can be returned by one path
expression.

A typical example of the above scenario is in traversal of links, for
example, you can have a book element which has author as children, and
also an IDREFS attribute called authors which points to person.
I believe such a path expression is valid -
book/(author | @authors -> person)
Now does this not require an order specification between child elements
and elements reachable through links? The reason is a user might expect
the same ordered result for the above expression as for the following
expression -
book (@author -> person | author)
Note that the above is possible even without an OR operator in the query.

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Received on Thursday, 28 September 2000 16:21:13 UTC

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