DDL.1: A Formal Description of a Constraint Representation Language for Physical Domains

This paper describes a domain description language DDL.1 able to represent physical domains to solve planning and scheduling problems. DDL.1 uses a representation, inspired by classical control theory, based on state-variables to represent the relevant features of a domain. Each state variable is meant to represent a set of plausible temporal evolutions those features may have. DDL.1 allows to specify constraints on the sequence of values that a state variable may assume over time. For the language a syntactic specification, and a model theoretic semantic are given. The problem of temporal planning using a DDL.1 specification is also addressed and a planning algorithm named TP-SV introduced. The paper tries to show how this kind of description languages may generate a methodology to gracefully model the relevant constraints in physical domains, and how a formally specified planner may be associated to this description.