- From: Axel Polleres <axel.polleres@deri.org>
- Date: Tue, 06 Nov 2007 18:15:56 -0500
- To: "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>

Evaluable predicates: The most general definition of external predicates (built-ins), I know of (in an attempt to write down the definition of Eiter et al. [1] in a RIF suitable way): An evaluable predicate &pred(X_1,....,X_n) is assigned with one or more binding patterns, where a binding pattern is a vector {in,out}^n. Intuitively, an evaluable atom provides a way for deciding the truth value of an output tuple depending on the extension of a set of input predicates and terms. Note that this means that 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.) External predicates have a fixed interpretation assigned. The distinction between input and output terms is made in order to guarantee that whenever all input values of one of the given binding patterns are bound to concrete values, the fixed interpretation only allows a finite number of bindings for the output values, which can be computed by an external evaluation oracle. 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. -- Dr. Axel Polleres email: axel@polleres.net url: http://www.polleres.net/

Received on Tuesday, 6 November 2007 23:16:14 UTC