Aggregate Functions in DLV (2003) [3 citations — 0 self]
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author = {Tina Dell'Armi and Wolfgang Faber and Giuseppe Ielpa and Nicola Leone and Gerald Pfeifer},
title = {Aggregate Functions in DLV},
booktitle = {Answer Set Programming: Advances in Theory and Implementation, volume 78 of CEUR Workshop proceedings, 274--288. Online: CEUR-WS.org/Vol78},
year = {2003},
pages = {274--288}
}
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Abstract:
Disjunctive Logic Programming (DLP) is a very expressive formalism: it allows for expressing every property of finite structures that is decidable in the complexity class 6790-45250 . Despite this high expressiveness, there are some simple properties, often arising in real-world applications, which cannot be encoded in a simple and natural manner. Especially properties that require the use of arithmetic operators (like sum, count, or min) on a set of elements satisfying some conditions, cannot be naturally expressed in classic DLP. To overcome this deficiency, we extend DLP by aggregate functions. In contrast to a previous proposal, we also consider the case of unstratified aggregates. We formally define the semantics of the new language (called DLP ) by means of a generalization of the Gelfond-Lifschitz transformation, and illustrate the use of the new constructs on relevant knowledge-based problems. We analyze the computational complexity of DLP showing that the addition of aggregates does not bring a higher cost in that respect. And we provide an implementation of DLP in DLV-- the state-of-the-art DLP system -- and report on experiments which confirm the usefulness of the proposed extension also for the efficiency of the computation. 1
