The unification of XML and SQL relational data has taken another significant step forward recently with the introduction of significant new XML functionality in mySQL, the world’s most popular open source database. In versions 5.1 and 6.0, mySQL adds the ability to retrieve tables (and JOINS) as XML results, to retrieve SQL schemas as XML files, to both select content via a subset of XPath and to update content using similar functions, and the like, as related recently in an article on the mySQL site: http://dev.mysql.com/tech-resources/articles/xml-in-mysql5.1-6.0.html .
I think the ramifications for this are actually quite huge. I’ve known for some time that much of the driving technology behind “Web 2.0″ is the power of SQL databases, with the bulk of those to date being mySQL databases. While enterprise level databases such as Oracle 10i+, IBM db2, and Microsoft SQL Server have long had XML capabilities, they also account collectively for a surprisingly small amount of the outward facing databases on the web, especially compared to mySQL. However, this has also has the unfortunate effect of promoting a relational database model as the prime one for the web, diminishing the utility of XML there and increasing the fragility of Web 2.0 applications.
With native XML support moving into mySQL, it opens up a chance for XML developers to start working within that community, and and also raises some significant issues with regard to how unstructured and semi-structured data is stored, retrieved and manipulated.
The XML support for mySQL is not yet at the level where it can support XQuery, but I think that this will come in time given the degree of support they have for the XPath specification. Keep an eye on this development; I think it will strengthen XML applications in general.
Thanks to Bill GIbbens of Influency for the initial heads up about the article.