A tool-supported approach to engineering HTN planning models

Our research concerns formal expressive, object centred languages and tools for use in engineering domains for planning applications. We extend our recent work on an object centred language for encoding precondition planning domains to a language called OCL/sub h/, designed for HTN planning. Domain encodings for HTN planners are particularly troublesome, because they tend to be used in knowledge 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 pre- and 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. We also define and illustrate a transparency property, together with a transparency checking tool, which helps the developer to encode a clear planning model in OCL/sub h/. Our encoding of the Translog domain is used as an extended example to illustrate the approach.