In-Depth

Last Call for XQuery

Time if running out for comments on XQuery, meaning a unified standard for querying structured and unstructured data is getting closer to approval.

• By Stephen Swoyer
• 12/10/2003

A unified standard for querying structured and unstructured data alike inched ever closer to reality last month when the World Wide Web Consortium (W3C) published still another working draft of the standard.

First proposed in 1998, the eXtensible Query Language (XQuery) 1.0 specification has been through more than half-a-dozen W3C Working Drafts and has already been revised three times in 2003.

The current revision of the proposed standard, published on November 12, has finally been elevated to W3C “Last Call” status and is currently subject to public review. This means that the XQuery Working Group believes that it has satisfied the technical requirements of the XQuery specification, as well as resolved any potential dependencies with other W3C groups. A Last Call announcement generally is one of the final stages before a Working Draft can be approved for W3C Candidate Recommendation.

XQuery is a complicated standard, but several related specifications are also in their Last Call Working Draft stages, including “XSL Transformations (XSLT) Version 2.0,” “XML Path [XPath] Language 2.0,” “XQuery 1.0 and XQuery 2.0 Data Model,” “XQuery 1.0 and XPath 2.0 Functions and Operators,” and “XSLT 2.0 and XQuery 1.0 Serialization.” Another specification, “XQuery 1.0 and XPath 2.0 Formal Semantics,” has not yet entered last call status, however.

The public review period for all of the XQuery-related Last Call Working Drafts is slated to end on February 15, 2004, at which point changes will be made to the specifications based on public recommendations. From there, it’s possible that the XQuery standard could be approved by the end of 2004—or sooner.

Crying Wolf

It’s been a series of setbacks for XQuery, which many supporters expected to be approved by the end of last year. Earlier this year, when several publications—including BI This Week—jumped the gun by reporting that the XQuery Working Draft would be elevated to Last Call status by the end of June, there was optimism that the standard might be finalized by the end of this year. At the time, a W3C representative told a major industry trade publication that she wouldn’t rule out seeing a finalized XQuery language by that time.

That rosy prognosis did not come to pass, however. In fact, a subsequent XQuery Working Draft was published on August 22—but many of the related XQuery specifications have been in Last Call for several months now, while XQuery itself has undergone more revisions this year than at any other point in its development. Now that XQuery 1.0 has officially been elevated to Last Call status, it’s not unreasonable to assume that there may finally be some light at the end of the tunnel.

Another encouraging sign: a definite show of support from major vendors in the form of productized implementations of XQuery. IBM Corp. has already introduced XQuery support in its DB2 Information Integrator product, a tool for enterprise information integration efforts—in other words, just what XQuery was designed for. In June, IBM Corp. and Oracle Corp. announced a Java Specification Request (JSR) to define a Java API in support of the emerging XML Query (XQuery) standard. A JSR serves as a request for submitting technologies as proposed standards for the Java programming language within the Java Community Process (JCP).

Meanwhile, some users, such as James Somers, a developer with Pro-Concept S.A., an ERP vendor based in Switzerland, are already using draft implementations of the XQuery standard in production system. “We use both XQuery and SQL/X [a language developed by Oracle to query unstructured data] to produce, transform, and consume XML documents representing complex and hierarchical data as ‘Customers,’ ‘Items,’ ‘Bill of Materials,’ and others. Those documents can come either from our own ERP or from other software.”

Although Somers and Pro-Concept adopted the XQuery standard at an early stage, he says he’s not worried about the Working Draft specification changing drastically between now and the time when it’s approved as a standard. “I think that even if the standard is not yet adopted, the drafts and the use cases won't change a lot. They may enlarge the standard … [but they will not change] the base structure of XQuery.”