COPLAS requires two pieces of information to run. A description of the domain where the planning is going to take place plus a goal. In this section we describe how domains are specified in the COPLAS language. We will refer to both the planner and the language to specify the domain as COPLAS. COPLAS has five classes of symbols: object symbols, type symbols, fluent symbols, non-sensing action symbols and sensing action symbols plus a countably infinite set of variables. Each fluent and action symbol has associated a positive integer called the arity of the symbol. A fluent is a term of the form f(t1,...,tn), where f is a fluent symbol and and each ti is either a variable or an object symbol. Similarly, a non-sensing action is a term of the form a(t1,...,tn), where a is a non-sensing action symbol and each ti is a variable or an object symbol. A sensing action is a term of the form a(t1,...,tn), where a is a sensing action symbol and each ti is a variable or an object symbol.
A domain description for COPLAS consists of four sections: the declaration of types, the action propositions, the axiom set and the initial situation description.