Re: Attempt to use Owl rule language to express preconditions in Congo

Drew McDermott wrote:

>   [Monika Solanki]
>   I am not sure, if this should be sent on www-ws, hence I am sending this 
>   only to the private list. David, pls let me know further.]
>
>I think it should be on www-ws, and am sending it there.
>
Thanks Drew!!!

>
>   ***** I have been trying to use the OWL Rule language,
>
>   http://www.cs.man.ac.uk/~horrocks/DAML/Rules/
>
>   for expressing the semantics of preconditions and effects in OWL-S.
>
>   ***** This is the first attempt at expressing preconditions as rules for 
>   the Congo Example.
>   ***** Feedbacks highly solicited.
>   ***** IN ORL (Owl Rule language), rules can be expressed as implications 
>   consisting of an antecedent and consequent.
>
Pls Note: This acronym for Owl Rule Language (ORL) has been cooked up by 
me for my own convinence. This is not standard

>  
>
>   The preconditions that we have for Congo Example are
>    ** Account Exists
>    ** Credit Exists
>
>   Semantically, the rule can be defined as, if a buyer has a valid Account 
>   and a valid Credit Card, he can buy a book from Congo.
>   So, we have as inputs to the book buying service, the following variables
>   1. Acct ID
>   2. Password
>   3. Creditcard Number
>   4. ISBN Number
>
>   Corresponding Input Classes,
>
>   <process:Input rdf:ID="AcctID"/>
>   <process:Input rdf:ID="Password"/>
>   <process:Input rdf:ID="CreditCardNumber"/>
>   <process:Input rdf:ID="ISBNNumber"/>
>
>   In ORL, we have to define "Variable" to be used in Rules.
>
>   <owl:Variable rdf:ID="AcctID"/>
>   <owl:Variable rdf:ID="Password"/>
>   <owl:Variable rdf:ID="CreditCardNumber"/>
>   <owl:Variable rdf:ID="ISBNNumber"/>
>
>   In our case the Input Classes are themselves variables. So we can write 
>   something like this,
>
>   <owl:sameIndividualAtom>   
>       <process:Input rdf:ID="AcctID"/>     
>       <process:Input rdf:ID="Password"/>
>       <process:Input rdf:ID="CreditCardNumber"/>
>       <process:Input rdf:ID="ISBNNumber"/>
>       <owl:Variable rdf:ID="AcctID"/>
>       <owl:Variable rdf:ID="Password"/>
>       <owl:Variable rdf:ID="CreditCardNumber"/>
>       <owl:Variable rdf:ID="ISBNNumber"/>
>   </owl:sameIndividualAtom>   
>
>   Now, we can define the rule as,
>
>   <!-- here the namespace congoUserProfile, holds the definition of 
>   classes and properties pertaining to a user of Congo -->
>   <owl:Rule>
>       <owl:antecedent rdf:parseType="Collection">
>	   <owl:individualPropertyAtom>
>	       <owl:propertyPredicate 
>   rdf:resource="&congoUserProfile;accountExists/>
>		   <owl:argument1 rdf:about="#AcctID" />
>		   <owl:argument2 rdf:about="#Password" />
>	   </owl:individualPropertyAtom>   
>	   <owl:individualPropertyAtom>
>	       <owl:propertyPredicate 
>   rdf:resource="&congoUserProfile;creditExists/>
>		   <owl:argument1 rdf:about="#AcctID" />
>		   <owl:argument2 rdf:about="#CreditCardNumber" />
>	   </owl:individualPropertyAtom>   
>       </owl:antecedent>
>       <owl:consequent rdf:parseType="Collection">
>       <owl:individualPropertyAtom>
>	   <owl:propertyPredicate 
>   rdf:resource="&congoUserProfile;allowedToBuy/>
>		   <owl:argument1 rdf:about="#AcctID" />
>		   <owl:argument2 rdf:about="#ISBNNumber" />
>	   </owl:individualPropertyAtom>   
>       <owl:Rule>
>
>   ***** Does this make sense ?
>
>The last bit does.  I don't know what the "sameIndividualAtom" stuff is.
>
I am not very clear on that either. What it is intended to imply is that 
the inputs are the actual variables for the rule. Maybe I need to put 
each of the input in a separate tag for sameIndividualAtom.  I have also 
sent the contents of this mail to Ian and Peter. I am sure, they would 
be able to provide a more clear interpretation of the  same.

>   ***** I would also like to discuss, if using rules in this way, helps in 
>   avoiding the use of rdf notations (DRS) for expressing logical formulae
>
>I don't understand.  The OWL Rule language _is_ RDF, at least
>syntactically.  It appears to use exactly the same tricks as DRS.  OWL
>Rule Language's "IndividualPropertyAtom" has precisely the same syntax
>and semantics as DRS's "Atomic_formula."  The only differences between
>DRS and ORL are (a) the way variables are handled; (b) the restriction
>in OWL Rules to unary or binary predicates.
>  
>
Thanks for the clarification.

>My assumption is that OWL-S should use ORL if at all possible
>simply because it is going to be the standard.  There may be a slight
>problem using ORL for preconditions and effects, because the former
>is like a rule with no consequent, and the latter like a rule with no
>antecedent; but we can use some ad hoc extension of ORL until the
>gods invent a notational variant of it and declare it to be elegant.
>
>  
>
-Monika

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Monika Solanki
Software Technology Research Laboratory(STRL)
De Montfort University
Hawthorn building, H00.18
The Gateway
Leicester LE1 9BH, UK

phone: +44 (0)116 250 6170 intern: 6170
email: monika@dmu.ac.uk
web: http://www.cse.dmu.ac.uk/~monika
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