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RE: Call for Participation: new internet draft for WebDAV SEARCH method

From: Julian Reschke <julian.reschke@gmx.de>
Date: Wed, 20 Feb 2002 12:37:01 +0100
To: "Amelia Carlson" <ameliac@us.ibm.com>, <www-webdav-dasl@w3.org>
Message-ID: <JIEGINCHMLABHJBIGKBCAEBNEBAA.julian.reschke@gmx.de>
Amelia,

thanks for the feedback...

> Hello,
>
> Here are two SQL-related points with respect to the draft for WebDAV
> SEARCH.
>
> 1. The reference to SQL92 should be updated to SQL99.  SQL200n is
> currently
> in
>      its final editing round, and will be available next year.
>
>     For SQL99, here's a citation:
>     Jim Melton (editor), ISO International Standard (IS),
>           "Database Language SQL Part 2: Foundation (SQL/Foundation)",
>           ISO/IEC 9075-2:1999 (E), July 1999.

Updated.

> 2. In the WebDAV SEARCH spec (5.6, DAV:orderby), it says that nulls sort
> low, to match SQL92.
>     However, SQL92 and SQL99 both say "Whether a sort key value that is
> null is
>     considered greater or less than a non-null value is
> implementation-defined,
>     but all sort key values that are null shall either be considered
> greater than
>     all non-null values or be considered less than all non-null values."
>     (words taken from SQL99, 14.1 <declare cursor> General Rule 2)c), in
>     reference to null handling for the <order by clause>. )
>
>     I would note that in 5.5.3 WebDAV SEARCH says nulls are less than all
>     other values in a comparison, so the DAV:orderby matches that
> statement,
>     it just gives an inaccurate reason.

Added to the open issues.

It seems to me that the draft tries to define different null treatment for
comparisons and ordering.

> Along other lines, has the use of XPath or XQuery for search been
> considered, and the XML-ized SQL choice made over them?

I've been playing with the concept of simply using XPath (1.0). This gives
you a powerful and easy to read syntax for the <where> part which also
solves many of the current limitations of DAV:basicsearch (like querying
into structured properties). In theory, XSLT 1.0 could be used for
constructing the results (like ordering). However, it's non-trivial to
implement XPath on top of a database.

DAV:basicsearch was designed to make it easy to forward the queries to a
standard SQL database, so *this* grammar shouldn't require anything a
standard data base can't give you.

Julian
Received on Wednesday, 20 February 2002 06:37:33 GMT

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