W3C XML Query Working Group published new documents

Several new W3C XML Query publications have hit the street the last weeks.

First of all the XML Query Working Group published a Candidate Recommendation of XQuery Update Facility 1.0. Together with this Candidate Recommendation, the Working Group published an update of the XQuery Update Facility 1.0 Requirements and XQuery Update Facility 1.0 Use Cases.

Where XQuery 1.0 only allows to "query", the XQuery Update Facility adds "update" capabilities to XQuery. The obvious use case is to update XML documents stored in a database, but XQuery Update Facility is about more! It also enables transformations and enrichment of both transient and persisted XML documents. Such operations are rather complex with XQuery 1.0. I will talk about some of these uses cases in a future post, and show what XQuery Update Facility adds to the XQuery world when it comes to transformations and data enrichment.

When will DataDirect XQuery support the XQuery Update Facility? If you were hoping to read here about an a concrete date, I have to disappoint you. All I can say right now is that DataDirect follows closely the XQuery Update Facility development process. We will be able to make this more concrete later this year, when the XQuery Update Facility moves into Proposed Recommendation. In the meantime, don’t forget that DataDirect XQuery offers today the ability to update your database through XQuery, Minollo blogged about a nice use case not so long ago.

I believe a significant limitations of the XQuery Update Facility is that an expressions is either "updating" or "non updating". In other words, within a single query it is not possible to both perform an update and return a query result. Looks like a common use case to me. The XML Query Working Group is trying to answer this through XQuery Scripting Extensions.

A first Working Draft of XQuery Scripting Extension 1.0 made it to the public recently. As this is a first Working Draft, don’t expect things to be written in stone. Everything is open for change and improvements. As with most of the XQuery specifications, this one also is accompanied by a Use Cases document, it provides the usage scenarios that motivate the changes in the XQuery Scripting Extension. I’m a fan of the use cases approach, it’s a good source for learning.

As said above, the ability to both "update" and "query" is required, and this is definitely the most important functionality I see in the XQuery Scripting Extensions. Some of the procedural extensions (assignments, while-loop, etc) are somehow questionable. It has to be seen how these will be used in a declarative language like XQuery. Will such concepts result in confusion for the user? Will productivity of XQuery programming improve through the procedural extensions? The future will tell...

The XML Query Working Group has been busy lately, and also started with XQuery 1.1. Still preliminary, but the Requirements and a first version of the Uses Cases were published mid March.