----- Ursprüngliche Message ----- > Von: Dave Reynolds <[email protected]> > An: [email protected] > CC: > Gesendet: 0:15 Dienstag, 6.August 2013 > Betreff: Re: Access list values in rules > > On 05/08/13 21:41, Igor Brussilowski wrote: >> Hi, thank you for reply. >> >> I sure know all these builtin functions but I'm not sure that they pass > to my case. May be I have to describe the scenario in more details. >> >> Here pseudo code: >> >> >> given (?s hasList ?list) >> if for all ?p in ?list >> >> (?s1 ?p ?o1) (?s2 ?p ?o2) equal(?o1 ?o2) >> then >> >> -> do smth > > No that's not directly possible in Jena rules since it involves implicit > negation (for all in the head). Jena is designed for monotonic deductive > closure. Jena does have the various non-monotonic hacks like noValue but > there is no real negation supported. > > However *if* your hasList values are fixed throughout the rule > processing then you could achieve this through rule compilation. > Pre-process your rule set to translate such a rule into: > > (?sa1 ?pa ?oa1) (?sa2 ?pa ?oa2) equal(?oa1 ?oa2) > (?sb1 ?pb ?ob1) (?sb2 ?pb ?ob2) equal(?ob1 ?ob2) > ... > -> do smth > > Where pa, pb etc are the fixed set of entries in your list. > > However, the equals in that case is pointless so this would be much > better as: > > (?sa1 ?pa ?oa) (?sa2 ?pa ?oa) > (?sb1 ?pb ?ob) (?sb2 ?pb ?ob) > ... > -> do smth
Right, indeed I do exact so in the builtin solution, the *equal* here was only to explain the evaluation logic. The hasList property (the owl:hasKey actually) delivers different lists for different classes in ontology, but these lists are then constant. I did not find how to iterate such lists in the rule definition, therefore I wrote the mentioned builtin to evaluate the lists at runtime in the java code, but as I said I'm afraid that this runtime rule processing is less performant, because it calls the Graph.find to evaluate the assertion (?s1 ?p ?o) (?s2 ?p ?o) for all ?p in the given ?list. Or is this really a legal way to do this? Another solution which I probed is to pre-compile the rules (as you also suggest) for different lists from ontology at startup. But I had difficult to setup this solution in the joseki's config file for reasoner initialization. Do you think this *pre-compile* solution would be better than the *runtime* one mentioned above? > > Since you have equals in there maybe you actually mean something > stronger than your pseudo code suggests. > >> I have already written a bultin function for this functionality (pseudo): >> >> (?s hasList ?list) >> -> myBuiltin(?s1 ?s2 ?list) >> >> >> but I have to do graph find within the builtin's headAction to get the > results of (?s1 ?p ?o1) (?s2 ?p ?o2) and I'm afraid that this decrease the > performance of the rule processing (or is it ok to do this?), therefore I'm > looking for rule optimization. > > The problem with that is the non-monotonicity. If some ?p value changes > then you would get a different result from your builtin but your rule > will not refire. > > Dave > >> >> Regards, >> Igor >> >> >> >> >> ----- Ursprüngliche Message ----- >>> Von: Joshua TAYLOR <[email protected]> >>> An: [email protected]; Igor Brussilowski > <[email protected]> >>> CC: >>> Gesendet: 20:50 Montag, 5.August 2013 >>> Betreff: Re: Access list values in rules >>> >>> On Mon, Aug 5, 2013 at 9:02 AM, Igor Brussilowski >>> <[email protected]> wrote: >>>> Hi all, >>>> >>>> I'm looking for how to access list items in a reasoner rule. > E.g the >>> pattern (?S owl:kasKey ?L) returns a list of all matching objects. Is > there any >>> way to access here the elements of the list for further processing, > e.g. to >>> print them all out? >>> >>> According to the documentation [1], there are a number of builtins for >>> working with lists: >>> >>> listContains(?l, ?x) >>> listNotContains(?l, ?x) >>> Passes if ?l is a list which contains (does not contain) the element >>> ?x, both arguments must be ground, can not be used as a generator. >>> >>> listEntry(?list, ?index, ?val) >>> Binds ?val to the ?index'th entry in the RDF list ?list. If there > is >>> no such entry the variable will be unbound and the call will fail. >>> Only useable in rule bodies. >>> >>> listLength(?l, ?len) >>> Binds ?len to the length of the list ?l. >>> >>> listEqual(?la, ?lb) >>> listNotEqual(?la, ?lb) >>> listEqual tests if the two arguments are both lists and contain the >>> same elements. The equality test is semantic equality on literals >>> (sameValueAs) but will not take into account owl:sameAs aliases. >>> listNotEqual is the negation of this (passes if listEqual fails). >>> >>> listMapAsObject(?s, ?p ?l) >>> listMapAsSubject(?l, ?p, ?o) >>> These can only be used as actions in the head of a rule. They deduce a >>> set of triples derived from the list argument ?l : listMapAsObject >>> asserts triples (?s ?p ?x) for each ?x in the list ?l, >>> listMapAsSubject asserts triples (?x ?p ?o). >>> >>> [1] http://jena.apache.org/documentation/inference/#RULEbuiltins >>> >>> -- >>> Joshua Taylor, http://www.cs.rpi.edu/~tayloj/ >>> >
