Querying MeSH with XQuery and SQL

This is the third in a series of posts on MeSH headings and how they can be manipulated in XML form in XML databases like SQL Server. Before reading this, you’ll want to read the previous post on loading the data, which in turn refers to the original post where I described the schema.

Loading MeSH into SQL Server 2005

One of the neat things you can do with many modern relational database servers is import and index hierarchically-structured XML data in a similar way as you would with tabular data — without ‘shredding’ it into tables and rows.

XSD schema for MeSH

The National Library of Medicine distributes the entire 25,000-node tree of MeSH descriptors (Medical Subject Headings) in XML form. Although they supply a DTD, many XML tools these days are designed to use XML schemas (aka XSDs) only.

I’ve converted the MeSH DTD into an XSD, starting with an automatic conversion using the W3C’s dtd2xsd.pl script, and then manually correcting the output. I haven’t done much XSD for a while so I’d be grateful for any feedback on it. I’ve included an explanation of the structure of MeSH because it has some subtleties that can make querying it rather confusing.