- From: Harry Halpin <hhalpin@w3.org>
- Date: Sun, 18 Jul 2010 18:23:43 +0100 (BST)
- To: "Juan Sequeda" <juanfederico@gmail.com>
- Cc: public-rdb2rdf-wg@w3.org
> Harry, > > On Sun, Jul 18, 2010 at 8:26 AM, Harry Halpin <hhalpin@w3.org> wrote: > >> While I enjoyed the talk last week, I was wondering about the >> relationship >> between Eric's proposed direct mapping [1] and the rules put forward >> last >> week by Marcelo [2]. This question goes to both, and the entire working >> group. >> >> One of the advantages of Eric's default mapping mechanism [1] is that it >> allows relational data to be expressed in RDF without the author of the >> mapping knowing *any* rules or having any ontology that he or she wants >> to >> map their relational data to. >> > > This is exactly the same as the Database-Instance-Only mapping. Are we sure? Eric - thoughts? There's at least two differences I see. Syntactically, ericP is not generating any new predicate URIs (foaf:name), thus his insistence on creating a "stem graph" with default URIs. I imagine this will just be a simple option, with the generateURIs being created by a call to some standardized interface to the Linked Data Web via a search engine like Sindice, a vocabulary management service, or something like OKKAM. The second difference is how Eric decided to express his semantics, i.e. using sets rather than Datalog-ish rules that resemble FOL. I went over Eric's work only once, but I believe we need to make a decision as a Working Group to pick one style of doing semantics and stick with it in the spec, even though they are technically equivalent, i.e. we should choose between set-theoretic model theory or just a mapping to FOL/Datalog/RIF semantics with a standard interpretation. It would be kind of odd to switch styles of semantics. > >> >> This is one of the requirements of our charter, although of course we >> want mappings to other vocabularies to be possible. Remember, this can >> be >> thought of as a two-step process, where the first step is a default >> mapping, and then later mappigs (via Datalog rules, RIF, SQL or >> whatever) >> could then transform >> > > In this simple approach, the predicates are the only things that are going > to be mapped: > > ex:name ->foaf:name > .... > > So you could have a system that can automatically generate: > > Triple(s, "ex:name", name) <- student(s_id, name), generateURI(s_id, s) > > or the user can write the mapping with the : > > Triple(s, "foaf:name", name) <- student(s_id, name), generateURI(s_id, s) > > >> Could we take the rules given earlier [2] and then use these to produce >> the same effects as Eric's direct mapping proposal? Could someone >> specify >> this in detail? >> >> > The Database-Instance-Only mapping does that. > > >> Then the default mapping could be seen as a certain default application >> of >> rules, an application that *can* be changed. >> > > The rules defines the semantics of what needs to be implemented in an > application > > >> >> cheers, >> harry >> >> [1] http://www.w3.org/2001/sw/rdb2rdf/directGraph/ >> [2]http://web.ing.puc.cl/~marenas/W3C/mapping_language.txt >> >> >> >> >
Received on Sunday, 18 July 2010 17:23:45 UTC