# Re: Representation of SWRL expressions in OWL-S

From: Manshan Lin <lmshill@gmail.com>
Date: Sun, 6 Feb 2005 21:12:39 +0800
Message-ID: <ced14a8405020605123ea985d6@mail.gmail.com>

```
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
> >>
> >>
> >> 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
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Received on Sunday, 6 February 2005 13:13:10 UTC

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