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

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
- as I understand it, the implementation of such built-ins is far from
trivial
- 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.

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. 90–96, 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
> 

-- 
Jos de Bruijn            debruijn@inf.unibz.it
+390471016224         http://www.debruijn.net/
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