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

From: Axel Polleres <axel.polleres@deri.org>
Date: Thu, 06 Dec 2007 23:57:25 +0000
Message-ID: <47588C65.70408@deri.org>
To: "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>

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 

"[...] 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. 

4. http://www.polleres.net/presentations/20071127-SPARQL++ODBASE2007.pdf

Dr. Axel Polleres
email: axel@polleres.net  url: http://www.polleres.net/
Received on Thursday, 6 December 2007 23:57:50 UTC

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