- From: Gary Hallmark <gary.hallmark@oracle.com>
- Date: Mon, 09 Mar 2009 14:18:29 -0700
- To: Christian de Sainte Marie <csma@ilog.fr>
- CC: kifer@cs.sunysb.edu, RIF WG <public-rif-wg@w3.org>
A variable can represent many values. E.g. ex:a(1) ex:a(2) forall ?x if ex:a(?x) then ex:b(?x) ?x is 1 and 2. Path expressions are just a shortcut for a variable. E.g. if _obj.slot > 2 and _obj.slot <= 5 then ... is short for forall ?z if _obj[slot->?z] and ?z > 2 and ?z <= 5 then ... Christian de Sainte Marie wrote: > Michael, > > Michael Kifer wrote: >> >> these things are called path expressions and they are not necessarily >> single-valued. For instance, FLORA-2 uses them alongside the frames, >> and they are simply shortcuts for some forms of conjunctions of frames. > > > I have taken the action to rework my proposal to separate the issues > of single-valued attributes, and path location. > > But that supposes that I understand how path locations can be > multi-valued: as much as I understand that, as atomic assertions, > frames that associate different values to the same object-attribute > pair can be true at the same time; as much I cannot understand how a > path expression, as a basic term, can represent more than one value. > Actually, dealing with single-valued attributes in a way that seemed > intrinsically appropriate for them - which frames are not - and that > is quite usual in object-oriented languages was the main reason for my > proposal. > > I mean, other basic terms, such as a constant symbol, a variable, or a > ground function call, represent, cannot represent but a single value: > how can a path expression, as a basic term, represent more than one? > Of course, it can be set-valued, but it still has a single value, > which is the set. > > Can you please clarify? An example would, also, certainly help me > understand better what you mean. > > Cheers, > > Christian > >
Received on Monday, 9 March 2009 21:19:27 UTC