Autonomous Agents and Multi-Agent Systems

, Volume 28, Issue 4, pp 682–719 | Cite as

An operational semantics for the goal life-cycle in BDI agents

  • James Harland
  • David N. Morley
  • John Thangarajah
  • Neil Yorke-Smith
Article

Abstract

A fundamental feature of intelligent agents is their ability to deliberate over their goals. Operating in an environment that may change in unpredictable ways, an agent needs to regularly evaluate whether its current set of goals is the most appropriate set to pursue. The management of goals is thus a key aspect of an agent’s architecture. Focusing on BDI agents, we consider the various types of goals studied in the literature, including both achievement and maintenance goals. We develop a detailed description of goal states (such as whether goals have been suspended or not), and a comprehensive suite of operations that may be applied to goals (including dropping, aborting, suspending and resuming them). We provide an operational semantics corresponding to this detailed description in an abstract agent language (CAN), and demonstrate on a detailed real-life scenario. The three key contributions of our generic framework for goal states and transitions are (1) to encompass both goals of accomplishment and rich goals of monitoring, (2) to provide the first specification of abort and suspend for all the common goal types, and (3) to account for plan execution as well as the dynamics of subgoaling. Our semantics clarifies how an agent can manage its goals, based on the decisions that it chooses to make, and further provides a foundation for correctness verification of agent behaviour.

Keywords

BDI agents Goal management Operational semantics 

Notes

Acknowledgments

We are grateful to an anonymous reviewer for this point. We thank Lin Padgham, Sebastian Sardiña, and the participants of the DALT’10 workshop for discussions. We thank the reviewers of the earlier versions of this article for thoughtful and detailed comments which have improved the work. JT acknowledges the support of the Australian Research Council and Agent Oriented Software Pty. Ltd. under Grant LP0453486. NYS acknowledges the support of the University Research Board of the American University of Beirut, and thanks the Operations group at the Judge Business School and the fellowship at St Edmund’s College, Cambridge. The work of DNM and NYS through SRI International was supported in part by the Defense Advanced Research Projects Agency (DARPA) under Contract No. FA8750-07-D-0185/0004. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of DARPA, or the Air Force Research Laboratory.

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Copyright information

© The Author(s) 2013

Authors and Affiliations

  • James Harland
    • 1
  • David N. Morley
    • 2
  • John Thangarajah
    • 1
  • Neil Yorke-Smith
    • 3
    • 4
  1. 1.RMIT UniversityMelbourneAustralia
  2. 2.SRI InternationalMenlo ParkUSA
  3. 3.American University of BeirutBeirutLebanon
  4. 4.University of CambridgeCambridgeUK

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