Diagnosis of Plans and Agents

Abstract

Abstract.We discuss the application of Model-Based Diagnosis in (agentbased) planning. Here, a plan together with its executing agent is considered as a system to be diagnosed. It is assumed that the execution of a plan can be monitored by making partial observations of the results of actions. These observations are used to explain the observed deviations from the plan by qualifying some action instances that occur in the plan as behaving abnormally. Unlike in standard model-based diagnosis, however, in plan diagnosis we cannot assume that actions fail independently. We focus on two sources of dependencies between failures: such failings may occur as the result of malfunctioning of the executing agent or may be caused by dependencies between action instances occurring in a plan. Therefore, we introduce causal rules that relate health states of the agent and health states of actions to abnormalities of other action instances. These rules enable us to determine the underlying causes of plan failing and to predict future anomalies in the execution of actions.

Diagnosis of Multi-agent Plan Execution

“…This paper describes a generalization of the model for plan diagnosis as presented in [18,16]. New in the current approach is (i) the introduction of primary and secondary diagnosis, and (ii) the introduction of objects representing actions, agents and equipment.…”

“…In [18,16], Witteveen et al describe how plan execution can be diagnosed by viewing action instances of a plan as components of a system and by viewing the input and output objects of an action as in-and outputs of a components. Here, we will use a modified version of the plan diagnosis proposed by Witteveen et al using a qualification κ of events (a, d, depth(a)) with a ∈ A.…”

“…Primary and secondary diagnosis is used to identify these causes. 3 To realize the benefits of plan-based diagnosis outlined above, we present in section 3 an adaptation of the object-oriented description of plan execution introduced in [18,16]. Section 4 shows how this object-oriented plan description enables the formalization of primary and secondary plan diagnosis.…”

“…To realize plan diagnosis, we adapt and extend the object oriented representation of plans presented in [18,16]. This representation has been chosen because it is more suited to plan diagnosis than the traditional plan representations such as [10,2,9,17] and it also enables us to extend the classical Model-Based Diagnosis (MBD) approach to the planning domain.…”

“…Witteveen et al [18,16] show how classical MBD can be applied to plan execution. To illustrate the different aspects of diagnosis discussed in the introduction, below we present an adapted and extended version of their formalization of plan diagnosis.…”