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   RE: [xml-dev] question on XQuery -> SQL translators

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Microsoft's SQLXML (http://msdn.microsoft.com/sqlxml) has provided the ability to perform XPath queries over relational data for a number of years. To answer the original questions
Q:  What is the input for this tool? - Is it the query/path expression and
the annotated XML Schema?

A: SQLXML uses Annotated XSD schemas to describe the relational <-> XML mapping and accepts XPath expressions that are used in queries.
Q: Also what XQuery/XPath operators are supported by this tool?
A: The following forum post http://dbforums.com/arch/73/2002/3/332022 describes the XPath features that weren't supported by the last version of SQLXML.
There is also IBM's Xperanto project (http://www.almaden.ibm.com/software/dm/Xperanto/index.shtml) which does something similar for XQuery.

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From: Mark R Maxey [mailto:Mark_R_Maxey@raytheon.com]
Sent: Monday, August 18, 2003 8:34 AM
To: xml-dev@lists.xml.org
Subject: Re: [xml-dev] question on XQuery -> SQL translators

Here're the ones I know of:
  • BEA Liquid Data (formerly Enosys)
  • Actuate (formerly Nimble)
  • Ipedo
  • HitSW Allora (beta will be out soon)
Additionally, Rainbow Engine has been claiming for a long time that a first release is imminent.

All build XML schemas based off of the RDBMS schemas and allow you to submit XQueries against them.  The all have different levels of support for the XQuery WDs, so functionality varies.

There are several good papers I'd recommend to learn how the query rewrite is performed:

Querying XML Views of Relational Data
Efficiently Publishing Relational Data as XML Documents
XML Queries and Algebra
The XQuery Formal Semantics: A Foundation of Implementation and Optimization

Murali Mani wrote:
Folks I have a quick question.

what are the tools which currently do this XQuery/XPath -> SQL

for each tool, I am looking for a quite broad picture, and these are 2
questions which I am particularly interested in..

(a) What is the input for this tool? - Is it the query/path expression and
the annotated XML Schema?
(b) Also what XQuery/XPath operators are supported by this tool? For
example, do they support descendant, if so, how do they do the
translation?? Also even for simple parent-child traveral in XPath, how
does the translator figure out what attribute/(s) to perform the join on??
(c) Of course, the next question is: do any of these tools try to do
minimization of the resulting SQL query, in other words, try to minimize
the number of unnecessary joins or other wasteful operations..

thanks and regards - murali.

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Mark Maxey


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