Norm, is it just me, or have you explained the abstraction from a database to a more general XML usage?

Is this just a database thing, or is it applicable more generally? XSLT|XQuery wise //x is frowned upon as wasteful. Is the 'universal index' the key to this, making it more usable?

regards DaveP

Because Mark Logic Server was built from the ground up to operate on XML, its indexing strategies are designed explicitly to work well with the full richness of mixed content. It's definitely the universal index that makes it possible for the server to provide immediate answers to a large number of query expressions (and different kinds of query expressions simultaneously) that would otherwise be slow to compute.

Of course, I don't mean to make it sound magical. It's possible to devise query expressions that ask questions that don't have answers in the index and those can't be answered instantly. Luckily, there are a whole bunch of dials and knobs on the server, so it's often possible to tailor the index to suit the queries you want to ask.

TANSTAAFL, the more things you index, the more space the database occupies. But compressed XML + indexes turns out not to be that much larger than the original XML.

Norm,

Any chance to have access to this application ?

MoZ

Not just at the moment. But maybe later in the year after the next version of the server officially ships.

Hi Norm, do you have a specified subset of the RDF/XML syntax that you use to store RDF in the XML database, to avoid the ambiguities and variations? And even if so, I suspect the XPath expressions to traverse RDF would still get hairy. You worked on RDF twig for this very reason. I wonder, does Mark Logic Server have a better way of handling RDF? I guess, optimally that would be SPARQL... 8-)

Parsing RDF in XSLT 2.0 or XQuery isn't too bad. Having user-defined functions and being able to call them in XPath expressions makes most of RDFtwig unnecessary.

I didn't do anything fancy, I just flattened all resources to single, separate nodes: no striping.

If you look at that through an XML lens and write some helper functions to work your way through bnodes, it's mostly ok.

I guess XPath 2.0 is pretty powerful, especially with preprocessing like you propose. I once created such a preprocessing (RDFXSLT flattening) step in XSLT, but I didn't have XPath 2.0 for the next step to make it really nice...

Anyway, I wanted to mention that there's this little thing that you might be interested in: it's called XSparql and it's a fairly straightforward combination of XQuery and SPARQL, so one can in a single query combine data from RDF (using graph patterns) and from XML, and output either XML or RDF (using SPARQL CONSTRUCT). (The link leads to a tech report and an online prototype, I'm among the authors.)

With your serious experience in XML and RDF, do you think such a combined language makes sense? Do you think it would be useful (no commitment from your employer necessary or even implied) to extend MarkLogic server with RDF capabilities, and if so, would a language like XSPARQL be a good way to access it?

Norm: I'm curious whether this all has led you to any new insights regarding XML Schema Languages and/or XML Query languages? Thanks.