A tool-supported approach to engineering HTN planning models

Our research concerns formal, expressive, objectcentred languages and tools for use in engineering domains for planning applications. In this paper we extend our recent work on an object-centred language for encoding precondition planning domains to a language called OCLh, designed for HTN planning. Domain encodings for HTN planners are particularly troublesome, because they tend to be used in knowledged-based applications requiring a great deal of ‘domain engineering’, and the abstract operators central to an HTN model do not share the fairly clear declarative semantics of concrete preand post condition operators. Central to our approach is the development, in parallel, of the abstract operator set and the hierarchical state specification of the objects that the operators manipulate. In this paper we define and illustrate a transparency property, together with a transparency checking tool, which helps the developer to encode a clear planning model in OCLh. Our encoding of the Translog domain is used as an extended example to illustrate the approach.