Sentential and diagrammatic representations are two different formalisms for describing domains and problems. Sentential descriptions are usually more expressive than diagrammatic ones, but tend to present a more complex and less intuitive notation. All modern planning domain description languages are sentential. The complexity of sentential formalisms has been of hindrance to the wider dissemination and take up of planning technology beyond the planning research community. This paper proposes a diagrammatic “meta-language” for planning domain descriptions based on setGraphs as an alternative to sentential languages. SetGraphs represent actions, states and goals in terms of set- and graph theoretic constructs. Through various practical examples, setGraphs are shown to yield simpler and more intuitive domain encodings, and to offer a high degree of elaboration tolerance. A theoretical analysis shows how the representation can be easily encoded using formal languages, and demonstrates that setGraphs are at least as expressive as a standard modern propositional planning domain description language. The model proposed constitutes a “core” representation that can be adopted as a basis for developing different planning domain description languages; it is suitable to be used across different levels of abstraction during the processes of language development and domain knowledge engineering, and it facilitates the elicitation, maintenance and re-use of planning domain descriptions
