David Lorenzo

JELIA Conference 2004 Conference Paper

Logic Programs with Functions and Default Values

• Pedro Cabalar
• David Lorenzo

Abstract In this work we reconsider the replacement of predicate-like notation by functional terms, using a similar syntax to Functional Logic Programming, but under a completely different semantic perspective. Our starting point comes from the use of logic programs for Knowledge Representation and Nonmonotonic Reasoning, especially under three well-known semantics for default negation: Clark’s completion, stable models and well-founded semantics. The motivation for introducing functions in this setting arises from the frequent occurrence of functional dependences in the representation of many domains. The use of functions allows us to avoid explicit axiomatization and provides a more compact representation by nesting functional terms. From a representational point of view, the most interesting introduced feature is the possibility of replacing default negation by the concept of default value of a function. In the paper, we explore this idea of functions with default values, providing adapted versions of the three mentioned semantics for the functional case, and equivalent translations into logic programs.

ECAI Conference 2004 Conference Paper

New Insights on the Intuitionistic Interpretation of Default Logic

• Pedro Cabalar
• David Lorenzo

NMR Workshop 2002 Conference Paper

Learning non-monotonic causal theories from narratives of actions

• David Lorenzo

Non-monotonic formalisms for reasoning about actions and change have become a whole subfield of Artificial Intelligence. Current implementations allow to work with very expressive action theories involving ramifications, concurrent actions, complex qualifications and so on. A natural question that can be posed is whether this kind of declarative knowledge can be learned from observed time traces of property values from an existing dynamic system. For this task we consider a narrative-based logical theory of change in the form of Extended Logic Programs where logic-based learning methods can be applied effectively. The use of a narrative formalism provides more expressivity on the theories that are learned, for instance, to learn the effects of concurrent actions.

ECAI Conference 2000 Conference Paper

Learning to Reason About Actions

• David Lorenzo
• Ramón P. Otero