[regrep] XQuery Support

["CHIUSANO, Joseph" <JCHIUSANO@lmi.org>]

Title: XQuery Support

Registry TC,

During our round of V3 brainstorming, I suggested XQuery support as a V3 item.  I cannot take credit for this as my idea, as there had been much discussion about it in the Query subteam during V2 efforts.  However, I'd like to provide some information on XQuery for those who may not be familiar with it.

I'm hoping that we can start debating on the advantages/disadvantages of introducing XQuery support into our architecture for V3.

Respectfully Yours,
Joe

What is XQuery?

• XQuery is a functional query language in which a query is represented as an expression


• It is based on OQL, SQL, XML-QL, and XPath


• Among XQuery's rich set of expressions is a "FLWR" expression - "For, Let, Where, Return"


• XQuery is a strongly typed query language - it uses W3C XML Schema simple types

How about an example?

• The following query (taken from the W3C XQuery main site) lists titles of books published by Morgan Kaufmann in 1998 - it uses 3 of the components of a FLWR expression:




FOR $b IN document("bib.xml")//book
WHERE $b/publisher = "Morgan Kaufmann"
    AND $b/year = "1998"
RETURN $b/title

What recommendation stage is XQuery currently at?

• As of 12/20/01, XQuery 1.0 became a W3C Working Draft

What is the realationship between XQuery and the new XPath 2.0 Working Draft?

• From the XQuery 1.0 W3C site:

The XPath 2.0 and XQuery 1.0 Working Drafts are generated from a common source. These languages are closely related, sharing much of the same expression syntax and semantics, and much of the text found in the two Working Drafts is identical.

• XPath 2.0 also became a W3C Working Draft on 12/20/01

Things for us to consider:

• The XQuery specification does not yet include updates, but they are planned in the future


• The XQuery 1.0 specification is still in the Working Draft stages, which means that it is not yet a fully stable W3C standard; this also *may* mean that few XML processors support it (pure speculation)


• Use of XQuery may allow for simpler query functionality in the XML Registry specification

Pertinent Web sites:

http://www.w3.org/TR/xquery/
http://www.w3.org/TR/xpath20/

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  Joseph M. Chiusano
  Logistics Management Institute
  2000 Corporate Ridge
  McLean, VA 22102
  Email: jchiusano@lmi.org
  Tel: 571.633.7722
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