Re: Representation of SWRL expressions in OWL-S

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.

Evren

Received on Friday, 4 February 2005 18:34:04 UTC