- From: Sergey Melnik <melnik@DB.Stanford.EDU>
- Date: Wed, 17 Nov 1999 12:18:27 -0800
- To: Janne Saarela <js@pro-solutions.com>
- CC: www-rdf-interest@w3.org
Janne, in my understanding RDF nodes cannot exist independently of the arcs they are hanging on. In this sense, the semantics of set operations is straight-forward: > For example: remove a model of one triple (A,B,C) from model (A,D,E). > Is the result an empty model or one single node E? > > Or: what is the intersection of (A,B,C) and (A,D,E)? {(A,B,C)} minus {(A,D,E)} = {(A,B,C)} {(A,B,C)} intersect {(A,D,E)} = {} {(A,B,C)} union {(A,D,E)} = {(A,B,C), (A,D,E)} etc. Thus, removing and adding nodes, i.e. specific resource URI, to the model is not necessary. However, thinking more about the core API, I'm tending to say that the set-oriented view on RDF models may be not appropriate in some circumstances. For example, if your models represent datasources a la Mozilla, it arguably may not make sense to intersect an email folder with a file system directory. The question is whether is it reasonable to reduce the core API even further, to remove union, intersection and difference and to place them into a separate interface that extends the core Model. Sergey
Received on Wednesday, 17 November 1999 15:13:58 UTC