[Attempto] ACE Wiki questions: How to represent plans, possible extensions to punctuation and API, and implementing non-OWL rules

[Norbert E. Fuchs]

On 20 Oct 2009, at 01:03, Murray, William R wrote:

> ...
>
> 2. I would like to represent a plan in ACE. Suppose I use a STRIPS- 
> like representation where each operator has preconditions and
> postconditions. Now suppose I have a simple three-step plan P, e.g.,
>
>      OP-1 OP-2 OP-3
>
> where each OP-i is an operator that is a plan step in plan P:
>
>     OP-1 is an operator.
>     OP-2 is an operator.
>     OP-3 is an operator.
>
> and add a new verb “assume” for each precondition...
>
>    OP-1 assumes resource X is available.
>    OP-2 assumes resource Y is available.
>    OP-3 assumes resource Z is available.
>
> and then add a rule like this
>
>    If a plan step O assumes a resource J is available and resource J  
> is not available
>    then plan step O fails.
>
> and overall rules so that any step of the plan failing causes the  
> whole plan
> to fail...
>
>   If a plan K has a plan step that fails then plan K fails.
>   If there is no plan step of K that fails then plan K succeeds.
>
> I don’t know if this is the right approach and would like other  
> suggestions.
>
> The first problem I run into is trying to represent the availability  
> of resources:
>
>    Resource X is available for OP-1.
>
> The best I could come up with are these two statements (rules):
>  <image001.png>
>
> where X would be a plan step and Y the overall plan and Z some  
> resource required for plan step X.
>
> Do you have any better suggestions? If I stay with this will SWRL  
> rules be produced when I export
> the code or do I have to handcode them?
>
> 3. How do I make statements that describe things? E.g., “Ranger  
> Company A is available.”
> It would seem that “available” is a non-transitive adjective and I  
> don’t see how to enter that as a new word.
> It seems only adjectives between nouns can be entered so I ended up  
> with “available for” above.
>
> But sometimes it would seem you’d simply need to save <noun> is  
> <adjective>, e.g., “the
> terrain is rough” or “the input is even”. How do you do that in ACE  
> Wiki?
>
> 4. Similarly, how do I enter standalone (intransitive) verbs? E.g.,  
> “OP-1 fails” and “Plan P fails.”

Bill, why do you want to do planning in SWRL rules? Wouldn't many of  
your problems disappear if you used ACE directly instead of AceWiki  
that – at least currently because of its use of the reasoner Pellet –  
offers only a subset of ACE geared towards translation into OWL?

> 5. I’m wondering how to use ACE grammar to represent events in time  
> and space:
>
> Does ACE allow describing the location and time of events, and what  
> is the best way to
> do this? I’d like to be able to have two statements such as “Ranger  
> Company A is at Kandahar
> at time T” and “Ranger Company A is at Melbourne at time T” and  
> conclude there is a contradiction.
>
> But I fear these kind of statements would not be in the ACE grammar  
> and in general I’d need a constraint checker
> to see if two locations are too far apart for the unit to move  
> between in the time specified. Something
> like a tie-in to CHR would be nice.

You can – as you already did – express time and location of events in  
ACE by prepositional phrases. You can express – as Tobias wrote –  
contradictions by additional axioms using logical negation. Again this  
might be easier in full ACE. Try this with the ACE reasoner RACE.

> ...
>

Regards.

    --- nef