Supporting Interleaved Plans in Learning Hierarchical Plan Libraries for Plan Recognition

Most of the available plan recognition techniques are based on the use of a plan library in order to infer user’s intentions and/or strategies. Until some years ago, plan libraries were completely hand coded by human experts, which is an expensive, error prone and slow process. Besides, plan recognition systems with hand-coded plan libraries are not easily portable to new domains, and the creation of plan libraries require not only a domain expert, but also a knowledge representation expert. These are the main reasons why the problem of automatic generation of plan libraries for plan recognition, has gained much importance in recent years. Even when there is considerable work related to the plan recognition process itself, less work has been done on the generation of such plan libraries. In this paper, we present an algorithm for learning hierarchical plan libraries from action sequences, based on a few simple assumptions and with little given domain knowledge, and we provide a novel mechanism for supporting interleaved plans in the input example cases.