[sc34wg3] TMQL, State of Affairs

Lars Marius Garshol sc34wg3@isotopicmaps.org
Tue, 24 May 2005 23:04:24 +0200

* Martin Bryan
| Then say so, and explain why TMDM is so radically different from
| every other data model in the universe that it needs its own query
| language.

As Jan and Murray are saying, I don't think it's that it is radically
different that causes this, but that simply the fact that it is
different. I can't think of any comparable data model that doesn't
have its own query language (relational -> SQL, XML -> XPath + XQuery,

| My point of view is that if it can be expressed in XML it can be
| queried using XQuery, and if it can be stored in a relational
| database it can be queried using SQL. 

Both of those statements are true, as Jonathan Robie's paper[1] and
TMRQL show quite clearly. That is rather different from it being
efficient to query topic maps using XQuery/SQL. And by efficient I
here mean two things: efficient for the person writing the query, and
efficient for the processor implementing it.

| If your statement implies that this model cannot be properly
| expressed in XML or stored in a relational database then people have
| a right to know.

They do, but it was not meant to imply that, but rather that query
languages for other models are inherently more difficult to use
because of the conceptual mismatch. I think the TMRQL proposal
illustrates this quite well, if you compare the solutions to the TMQL
use cases in it with those written in the proposed topic map-based
query languages (as Robert did in his article).

The same applies to XQuery, and much more so if we are talking about
XQuery on XTM, since XTM is horrible to query with XPath/XQuery.

[1] <URL: http://www.w3.org/XML/2002/08/robie.syntacticweb.html >
[2] <URL: http://www.networkedplanet.com/download/TMRQL.pdf >

Lars Marius Garshol, Ontopian         <URL: http://www.ontopia.net >
GSM: +47 98 21 55 50                  <URL: http://www.garshol.priv.no >