Re: [topicmaps-comment] mapping topic maps on a relation database

[Murray Altheim <m.altheim@open.ac.uk>]

Lars Marius Garshol wrote:

> * franck legoux
> | 
> | Does someone has a model to map "topic maps" on a relational
> | database ?
> 
> * Andreas Rittershofer
> | 
> | This is possible, but why not to store it in an XML-database like
> | Xindice? See http://xml.apache.org
> 
> You could do that, but the benefit is much smaller than it seems.
> Basically you would have to create a new DTD (call it XTM') and then
> transform from XTM to XTM' before storing it. Otherwise performing
> simple queries like "show me all composer born in Italy" is just plain
> hell to compute, since you would have to do things like merging,
> following three different kinds of references etc during the query
> evaluation.


Unless you always stored already-merged topic maps. But you're
correct, this isn't a simple matter of storing an XML document.
But simple queries of an already-merged topic map (such as "get
all topics whose base name is 'harrier' in the scope of 'birds'"
can certainly be done. You just need to be sure that the TM engine
is hooked into the DB correctly when TMs are brought in and merges
are requested. [I'm not looking forward to this part of my future...]


> Using an XTM' DTD may be a viable option, but I think you'd find XML
> Query about as easy to use for querying it as SQL for querying the
> RDBMS topic map. 
> 
> What you really want is a frontend that hides all the messy storage
> details for you. All the topic map engines do this for you, in one way
> or another. TM4J even has an XML storage option, but I don't know what
> DTD that uses. The commercial ones also have RDBMS storage solutions,
> but none of them publish their schemas, as far as I know.


Kal used the Ozone XML database, so it's only a matter of work to
reengineer it to use Xindice.

Murray

......................................................................
Murray Altheim                         <mailto:m.altheim @ open.ac.uk>
Knowledge Media Institute
The Open University, Milton Keynes, Bucks, MK7 6AA, UK

      In the evening
      The rice leaves in the garden
      Rustle in the autumn wind
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