- From: Daniel Elenius <elenius@csl.sri.com>
- Date: Fri, 04 Feb 2005 10:06:09 -0800
- To: Bijan Parsia <bparsia@isr.umd.edu>
- CC: "daml-process@bbn.com" <daml-process@bbn.com>, public-sws-ig@w3.org
Bijan Parsia wrote: > On Feb 4, 2005, at 1:35 AM, Evren Sirin wrote: > >> Daniel Elenius wrote: > > [snip] > >>> >> I have two concerns about this format: >> >>> >>> 1) Aren't all SWRL expressions supposed to be instances of the >>> http://www.daml.org/rules/proposal/swrl.owl#Imp class? >> >> >> No, a SWRL expression body is supposed to be an AtomList which is >> simply the conjunction of atoms in the list. > > > By design. > Where is this design defined? I can see that the body and head of an Imp are AtomLists, but is there any semantics (or rules, whatsoever) for having SWRL expressions that are not rules (Imps)? Is there some secret document that I should be looking at? (I've only read the one at http://www.daml.org/rules/proposal/). >>> 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! > Yes, but wouldn't an empty *head* do it? >>> 2) If this is not the case, i.e. we can use constructs from SWRL as >>> we feel like it, >> >> >> No, we can not. > > [snip] > > Definitely not. The intention was that you'd use SWRL constructs in > the relevant *ontologies*. So *outside* and expression, you can use > SWRL rules as you see fit. > > Cheers, > Bijan.
Received on Friday, 4 February 2005 18:06:17 UTC