<- I've done quite a bit of thinking about it; got some paper notes which <- I'm in the (slow) process of typing up. You're right, there's a simple <- mechanical mapping of rows in a table to RDF; what you lose by this is <- the natural linking of properties. Not sure I understand - linking of properties in the RDF? <- For a sufficiently normalised relational schema*, you can generally <- produce a mapping <- (primary key) -> resource <- (other values) -> properties <- (foreign key) -> link to resource representing primary key for <- foreign table Great - this looks very promising, just the kind of thing I was looking for, I'm going to have to get pencil & paper. <- * that is, very (what, fifth NF?): for instance, moving one-to-one data <- into a separate table if the data describes a separate concept; it's <- generally possible to produce a normalised schema from a less normalised <- (ie, more real-world) one with the judicious use of views. Ugh! I've been postponing re-reading on the later NFs, hoping I wouldn't have to. Rats. I foolishly didn't say what I was wanting to do with the mapping - off list I've been mailed some good links for going RDF -> RDBMS (thanks!), but I'm really looking at RDBMS -> RDF and (as you seem to have mind-read) was wondering whether there was a way up from relational <-> RDF model. The plan is to expose a RDBMS, starting with metadata, trying to preserve as much of the logical structure as possible. I'm currently thinking this way : pump out the top-level information as RDF, linked down to a dynamically generated XML Schema that will pass on the constraints for any actual data requested, which will in turn be presented as straight XML. I reckon if I can get the RDF right, the rest should follow mechanically. Hopefully ;-) I was considering doing the mapping within the DB, generating a table of triple using the logical capabilities of the RDBMS. This is very appealing from the point of view of integrity (& probably efficiency), but the stuff will still need to be poured out in a form that other systems will understand, and application-level constraints will almost certainly be needed at the other end anyway, so it's code-hacking time whatever happens. Thanks for the info. Now where's that pencil...Received on Thursday, 3 May 2001 13:03:21 UTC
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