- From: Manshan Lin <lmshill@gmail.com>
- Date: Sun, 6 Feb 2005 21:12:39 +0800
- To: public-sws-ig@w3.org
On Fri, 04 Feb 2005 13:33:35 -0500, Evren Sirin <evren@cs.umd.edu> wrote: > > Bijan Parsia wrote: > > >>> I know that this was the case in an intermediate > >>> version of OWL-S, but this version does not seem to be available > >>> anymore. Expressions were rules with > >>> empty heads (bodies?). > >> > >> > >> I think at some point it was considered to use rules with empty > >> bodies. Then the expression would be written as the head of the rule. > >> SWRL defines empty body to be trivially true so the implication is > >> true whenever the head is true. But using rules in this way would be > >> more confusing so it was decided to use AtomList's directly. > > > > > > It's not just confusing, it's the wrong semantics, right? Precondtions > > *aren't* always true! > > It is not wrong semantics. Maybe I wasn't clear before. The idea is to > use a rule "<empty body> implies Precondition" in the precondition > expression. This implication is true only when "Precondition" is true so > logically it is same. But I don't think anybody looking at a SWRL rule > "p implies q" would first think it as "not(p) or q". This is why I'm > saying it is confusing to use SWRL rules in this manner. Can we use SWRL to define universal quantifier? For example, all (x) ( A(x) and P(a,x) ) (B(x)) can be defined as ( A(x) and P(a,x) ) implies (B(x)) . In this case, "x" is an universal variable. -- Best regards! Manshan Lin (林满山) Email: lmshill@hotmail.com;lmshill@gmail.com;lms-hill@21cn.com Affiliation: School of Computer Science and Engineering, the South China University of Technology Phone: (+86)13711287277 2005-02-06 ---------------------- \ " ___0__/ | /_ | .__/ \_. |
Received on Sunday, 6 February 2005 13:13:10 UTC