Agent Programming with Declarative Goals

Abstract

A long and lasting problem in agent research has been to close the gap between agent logics and agent programming frameworks. The main reason for this problem of establishing a link between agent logics and agent programming frameworks is identified and explained by the fact that agent programming frameworks have not incorporated the concept of a declarative goal. Instead, such frameworks have focused mainly on plans or goals-to-do instead of the end goals to be realised which are also called goals-to-be. In this paper, a new programming language called GOAL is introduced which incorporates such declarative goals. The notion of a commitment strategy -one of the main theoretical insights due to agent logics, which explains the relation between beliefs and goals -is used to construct a computational semantics for GOAL. Finally, a proof theory for proving properties of GOAL agents is introduced. Thus, we offer a complete theory of agent programming in the sense that our theory provides both for a programming framework and a programming logic for such agents. An example program is proven correct by using this programming logic.

GOAL as a Planning Formalism

“…The agent programming language Goal is a language for programming rational agents [10,4]. It provides constructs for specifying the beliefs and goals of agents and for programming a strategy for action selection.…”

“…Temporal Goal has been introduced in [10] but here we use a first-order variant and show how planning problems with temporal planning constraints can be embedded in Goal. The KRT plugin of temporal Goal is L LT L , |= LT L , ⊕ where L LT L is a first-order linear temporal language and |= LT L is the usual consequence relation associated with L LT L [7].…”

“…Temporal Goal uses an encoding of action specifications or planning operators into L LT L as in [5,10,11]. This allows us to incorporate a declarative encoding of action preconditions and effects in the knowledge base of a Goal agent.…”

“…L Ψ and |= Ψ are as defined above, given that L = L LT L . L Ψ thus allows temporal formulae inside the scope of the B and G operators, and we can use this to define several common sense notions of goals (see also [10]). Let goal χ be short for Gχ ∧ ¬Bχ.…”

“…The main contribution of this paper is to formally show that the agent programming language Goal [10] can be used as a planning formalism. Goal agents are BDI agents that derive their choice of action from their beliefs and goals.…”