[rules-users] JBoss Drools evaluation

[Mark Proctor]

On 8 Jul 2013, at 13:38, Wolfgang Laun <wolfgang.laun at gmail.com> wrote:

> On 08/07/2013, Mark Proctor <mproctor at codehaus.org> wrote:
>> 
>> On 8 Jul 2013, at 08:03, Wolfgang Laun <wolfgang.laun at gmail.com> wrote:
>>> Some backward chaining functionality is indeed available, although it
>>> cannot be compared with what you have in, say, Prolog.
>> that might be an undersell. We do full derivation tree's, as per prolog. But
>> we take this a step further, and have fully reactive derivation trees -
>> which most prolog systems does not have.
>> http://www.youtube.com/watch?v=fCjIRVSRFvA
>> 
>> The prolog features we do not have are:
>> cut
>> List unification.
>> Unbound properties  for fact instances. So that it unifies against the
>> property.
>> Expressions for arguments in unifications.
>> 
> 
> What about arithmetic? Is this what you mean with the last item, e.g.
>  fact(0,1).
>  fact(N,R):- fact(N1,R1),N is N1+1,R is R1*N.
yes, right now you can't do the following as an argument: X + Y / 2

This is not a limitation of the backward chaining algorithm implementation, and can be easily added in the future.

Mark
> 
> It's OK to expect a hybrid system to have facets not present in one or
> the other "pure" system. There's a considerable number of exercises
> you can do in Prolog, but can't do in Drools  - and the other way
> round, to be sure!
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