Agent Dynamic Logic (ADL) and
Operational semantics for agent programming languages


Wayne Wobcke
School of Computer Science and Engineering
University of New South Wales

9-30am - 11am,
RMIT University Function Room (near Kaleide Theatre)
Building 8, level 2, RMIT,
Swanston Street, Melbourne.

Abstract:

In recent years, there have been increased efforts towards defining rigorous operational semantics for a range of agent programming languages. At the same time, there have been increased efforts to develop logical frameworks for modelling belief, desire and intention (and related notions) that make closer connections to the workings of particular architectures, thus aiming to provide some computational interpretation of these abstract models. However, there remains a substantial gap between the more abstract logical approaches and the more computationally oriented operational approaches. In this paper, we aim to bridge this gap for a class of agents whose architecture and programming language is based on the PRS system. We first develop an operational semantics for a simplified 'PRS-like' agent architecture, abstracting some common features of this class. We then present a new logical framework called Agent Dynamic Logic (ADL) that combines BDI Logic and Propositional Dynamic Logic, and show how ADL can be used to model the 'mental states' of PRS-like agents (their beliefs, desires and intentions) and the semantics of their agent programs. The modelling allows a mapping between the states in the operational description of the PRS-like architecture and the models in the logical semantics of the agent's mental states, thus bridging the gap between the two levels of description for this class of architectures. Finally, we consider the logical properties of intentions and various rationality postulates for PRS-like agents that are a consequence of this modelling, in particular Bratman's asymmetry thesis, the side effect problem for intentions and Rao and Georgeff's non-transference principles. We show that PRS-like agents do enjoy many of the accepted logical properties of intention and rationality postulates as automatic consequences of our approach, though we argue that PRS-like agents do not have intentions in the sense required by Bratman's theory.

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