- From: Phillip Lord <phillip.lord@newcastle.ac.uk>
- Date: Tue, 19 Sep 2006 14:53:24 +0100
- To: "Kashyap, Vipul" <VKASHYAP1@PARTNERS.ORG>
- Cc: <public-semweb-lifesci@w3.org>, <semantic-web@w3.org>
>>>>> "KV" == Kashyap, Vipul <VKASHYAP1@PARTNERS.ORG> writes: >> There are two different things in the technologies you mentioned; >> relational to X mapping tools, and metaschema approaches. They >> are quite different. For the instance store, the relational >> database is really an implementation detail. It's basically a >> reasoner with somewhat limtied expressivity which is persistent >> and (hopefully) scalable. KV> [VK] Is this true only for TBox reasoning, or ABox and TBox KV> reasoning? I had the impression (possibly mistaken) that ABox KV> reasoning takes advantage of the relational backend. At least KV> this is implied by the following snipper >From an earlier KV> e-mail: The instancestore (or at least the very early version that I implemented) only does T-Box reasoning technically. The "A-Box" is stored in a relational database. It works like this -- when an instance is asserted (described) the reasoner is used to localise it's description in the ontology. This data is then denormalised and put into the database. So, for example, if you have an entirely asserted hierarchy, you should be able to get all instances of a given class without (very much) reasoning. In other, more complex, cases individuals have to be reasoned over quite a lot at both insert and query phases. The reason that it works is because you can't assert relationships between individuals, so you never need to re-reason things about instances. For example, imagine these assertions phil hasSibling martin This makes me a member of the class of things which have siblings. Next we assert martin hasSex Male Now, my own definition may have changed -- I am a member of the class of things which have brothers. So the new insert potentially requires updating our understanding of all instances. But with the instance store you can't make the first assertion, only things of the form of the second, so you are safe. As I said, this was true of the first instancestore. The current version is cleverer and can make some assertions of the first form. You'd have to ask others for details of this. KV> [VK] I guess I need to get out of my laziness and read the KV> paper, but how different is the metaschema approach from the X KV> to relational mapping approach? It's a metaschema -- every ontology uses the same schema. For a relational mapping, you'd expect different ontologies to use different ones. KV> Even if it is a very different approach, is it able to leverage KV> the "scalability features" of an RDBMS enumerated above? I would KV> be interested in your responses. The instancestore uses indexes, yes. This is actually easier -- you have only one schema, so the appropriate indexes are the same for every ontology. Phil
Received on Tuesday, 19 September 2006 14:16:54 UTC