[iris-reasoner-support] Built-ins and Bug(?)

[Murat K. <mur...@st...>]

Hi,

I have a question regarding built-ins. Having taken a look at the source 
code, I would like to understand why the following datalog programs do 
not work as (I) expected. (They are appended below.)

Program 1 works as expected, but 2 and 3, on the other hand, do not. 
With 2 I expected to get the correct answer to the calculation, i.e. 24. 
Program 3 was supposed to deliver 6, obviously. This ought to be 
possible through the IRIS feature of deducing the last number involved 
e.g. in a ternary mathematical predicate, but which also applies to the 
EQUAL-predicate.

My explanation is that, after building the knowledge base, the facts are 
all that is left - the rules are not looked at again during query 
evaluation. This results in the might of the UNIVERSE variable, which 
ought to solve problems like program 3, to get lost . It also leads to 
the deduction capabilities of the EQUAL-predicate to not be applied to 
the constant in the query - producing an empty result set.

Is my understanding of the matter correct?


And I would like to know if the following is a bug or intended behavior.
FiniteUniverseFact: The method

void extractGroundTerms( Collection<IRule> rules )

twice extracts the ground terms from the rule's head but never from the 
body. I suppose this is a copy-and-paste error?
http://iris-reasoner.svn.sourceforge.net/viewvc/iris-reasoner/iris/trunk/src/org/deri/iris/facts/FiniteUniverseFacts.java?view=markup&pathrev=1593

Thanks,
Murat


==== 1. ====
pred1('p1' , 'p2').
pred2('p2' , 'p3').
pred(?X,?Z) :- pred1(?X,?Y), pred2(?Y,?Z).
?-pred('p1',?X).
----------------------------------
Query:      ?- pred('p1', ?X). ==>> 1 row in 0ms
Variables:  ?X
('p3')


==== 2. ====
some_calc(?X,?Z) :- MULTIPLY(?X,?X,?Y), ADD(?Y,-1, ?Z).
?-some_calc(5,?Z).
----------------------------------
Query:      ?- some_calc(5, ?Z). ==>> 0 rows in 0ms
Variables:  ?Z


==== 3. ====
eq_ordinary(?x, ?y) :- EQUAL(?x,?y).
?-eq_ordinary(6,?q).
----------------------------------
Query:      ?- eq_ordinary(6, ?q). ==>> 0 rows in 0ms
Variables:  ?q