Re: [iris-reasoner-support] Request for support

[Barry B. <bar...@st...>]

Hi Thomas,

Thanks for your interest in IRIS!

I've had a look at your program and have some comments. First of all,
anything in quotes (single or double) is interpreted as a string. So
these values won't give any results when used with arithmetic built-ins
predicates.

Numbers with no '.' are assumed to be integers and numbers with a '.'
are double precision, i.e. java 'double' type. You can even be more
specific by using constructors, e.g. _float(1.2), _decimal(3), etc.

Assuming you want to use floating point numbers, I re-wrote your program to:

database(1.0, 10.0, 100.0).
database(2.0, 5.0, -10.0).

score(?s, ?x1, ?x2) :- 3 * ?x1 =?wx1, 2 * ?x2 = ?wx2, ?wx1 + ?wx2 = ?s.

ds(?id, ?s) :- database(?id, ?x1, ?x2), score(?s, ?x1, ?x2).

?-ds(?id, ?s).

However, I'm not sure what you are trying to do. Certainly, the rule
with "score(?s, ?x1, ?x2)" in the head is un-safe (unbound head
variables). IRIS can be configured to handle un-safe rules, however, but
it seems you are trying to 'pass' values for ?x1 and ?x2 and 'return'
something for ?s, i.e. use score() like a function call. This may be
possible in proper logic programming, but sadly not so in simple'ish
Datalog.

However, if you combine the two rules:

database(1.0, 10.0, 100.0).
database(2.0, 5.0, -10.0).

ds(?id, ?s) :- database(?id, ?x1, ?x2), 3 * ?x1 =?wx1, 2 * ?x2 = ?wx2,
?wx1 + ?wx2 = ?s.

?-ds(?id, ?s).

Then you get rid of the unsafe rule and this computes quite nicely:

Query:      ?- ds(?id, ?s). ==>> 2 rows in 0ms
Variables:  ?id, ?s
(1.0, 230.0)
(2.0, -5.0)

I hope this helps,
barry

-- 
Barry Bishop
Senior Scientific Programmer
Semantic Technology Institute (STI)
University of Innsbruck, Austria
-----------------------------------
E-Mail: bar...@st...
Tel:    +43 512 507 96873
-----------------------------------


Thomas TRIPLET wrote:
> Hello all !
> 
> I need to use Datalog and I found IRIS which looks like it is exactly
> what I am looking for.
> 
> I'm kinda struggling with the syntax though. this should work but does not:
> 
> database('1', '10', '100'). database('2', '5', '-10'). score(?s, ?x1,
> ?x2) :- 3 * ?x1 =?wx1, 2 * ?x2 = ?wx2, ?wx1 + ?wx2 = ?s. ds(?id, ?s) :-
> database(?id, ?x1, ?x2), score(?s, ?x1, ?x2). ?-ds(?id, ?s).
> 
> I
> have a database with an id and 2 values for each. I need to computer a weighted sum of those values for each id and return the sum.
> But for some reason, this doesn't work. It's working with another Datalog interpreter (MLPQ) so I am not sure what I am missing here.
> 
> By the way does anyone know if IRIS uses double or simple precision for numbers?
> 
> 
> Thanks for any input!
> Thomas
> 
> --
> Thomas Triplet
> PhD student - Bioinformatics
> Computer Science and Engineering Department
> University of Nebraska - Lincoln, USA
> 
> 
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