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Re: ACTION-384 completed: Post a use case for Higher-order builtins

From: Chris Welty <cawelty@gmail.com>
Date: Tue, 11 Dec 2007 10:35:38 -0500
Message-ID: <475EAE4A.6040205@gmail.com>
To: Jos de Bruijn <debruijn@inf.unibz.it>
CC: axel@platon.escet.urjc.es, "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>


Is Axel not responding to the list or am I dropping more email?  I am only 
seeing Jos' half of this discussion.

-Chris

Jos de Bruijn wrote:
>>> It seems to me that this is an issue for phase 2:
>>> - I do not think there are many systems which support this kind of
>> built-ins
>>
>> well, aggregates are supported by many languages (SQL, XQuery, etc.)
>> and of crucial importance. It is just a more general definition of
>> built-ins, fully upwards-compatible to simply saying "predicates with a
>> fixed interpretation". I see no reason to preclude it if we can accomodate
>> it by a slightly more general notion of built-ins.
> 
> The languages you mention are query languages; not rules languages. Are
> there any rule systems besides dlvhex which support such general built-ins?
> 
>>> - as I understand it, the implementation of such built-ins is far from
>>> trivial
>> not so hard either.
>>
>>> - because time is short, I think we should not start introducing new
>>> features in the language, but rather concentrate on finishing the
>>> features we agreed upon so far.
>> It is important to avoid lock-in against such features though.
> 
> it would be good to leave the option open for possible future extensions.
> 
> Best, Jos
> 
>> Did you answer this to me only, or to the list?
>>
>> Axel
>>
>>
>>> Best, Jos
>>>
>>> Axel Polleres wrote:
>>>> Hi all,
>>>>
>>>> I was asked to make a use case for what is called higher-order built-ins.
>>>>
>>>> In order to recap, let me repeat a generic definition of the term
>>>> "built-in" from one of my previous mails (see
>>>> http://lists.w3.org/Archives/Public/public-rif-wg/2007Nov/0011.html):
>>>>
>>>> "[...] evaluable predicates, unlike usual definitions of built-ins in
>>>> logic programming, can not only take constant parameters but also
>>>> (extensions of) predicates as input. Inputs can not only be terms, but
>>>> also predicate names (in which case the *extension* of the respective
>>>> predicate is the input.)"
>>>>
>>>>
>>>> Here some example:
>>>>
>>>>
>>>> 1) Aggregate functions, for instance count seem to be a necessary
>>>> prerequisite for aggregating not only database data, but also web data:
>>>> In this example, we assume we have a builtin &count with binding pattern
>>>>
>>>>   &count( Input, Output)
>>>>
>>>> available that counts the extension of the predicate 'Input'. With such
>>>> a predicate, I could count the number of foaf:knows links defined in my
>>>> foaf file more or less like this:
>>>>
>>>>     myfriends(?X) :- :me[foaf:knows->?X].
>>>>
>>>>     friendscount(Count) :- &count( myfriends, Count ).
>>>>
>>>>   Such builtins ar implemented in the dlvhex system [1,2]. We used this
>>>>   generic mechanism for instance to implement an extension by aggregate
>>>>   functions for SPARQL, details see [3,4]. In that paper we have more
>>>>   complex agregates where we can also define the parameters of a certain
>>>>   predicate we want to agregate over.
>>>>
>>>> 2) Another example is interoperability of rules and ontologies by
>>>> dedicated DL query predicates, see also [1].
>>>>
>>>>
>>>> 1. 1. T. Eiter, G. Ianni, R. Schindlauer, H. Tompits. A Uniform
>>>> Integration of Higher-Order Rea-
>>>> soning and External Evaluations in Answer Set Programming. In
>>>> International Joint Con-
>>>> ference on Artificial Intelligence (IJCAI) 2005, pp. 9096, Edinburgh,
>>>> UK, Aug. 2005.
>>>>
>>>> 2. http://www.kr.tuwien.ac.at/research/dlvhex
>>>>
>>>> 3. A. Polleres, F. Scharffe, and R. Schindlauer. SPARQL++ for mapping
>>>> between RDF vocabularies. In OTM 2007, Part I : Proceedings of the 6th
>>>> International Conference on Ontologies, DataBases, and Applications of
>>>> Semantics (ODBASE 2007), volume 4803 of Lecture Notes in Computer
>>>> Science, pages 878-896, Vilamoura, Algarve, Portugal, November 2007.
>>>> Springer.
>>>> http://www.polleres.net/publications/poll-etal-2007.pdf
>>>>
>>>> 4. http://www.polleres.net/presentations/20071127-SPARQL++ODBASE2007.pdf
>>>>
>>
> 

-- 
Dr. Christopher A. Welty                    IBM Watson Research Center
+1.914.784.7055                             19 Skyline Dr.
cawelty@gmail.com                           Hawthorne, NY 10532
http://www.research.ibm.com/people/w/welty
Received on Tuesday, 11 December 2007 15:35:56 GMT

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