CTL AgentSpeak(L): A specification language for agent programs

APPIA-GULP-PRODE, 2002

Research on tools for modeling and specifying intelligent agents, namely computer systems situated in some environment and capable of flexible autonomous actions, is very lively. Due to the complexity of intelligent agents, the way they are modeled, specified and verified should greatly benefit by the adoption of formal methods. Logic-based languages can be a useful tool for engineering the development of a multi-agent system (MAS). This paper discusses six logic-based languages which have been used to model and specify agents, namely ConGolog, AGENT-0, the IMPACT specification language, Dylog, Concurrent METATEM and. To show their main features and to practically exemplify how they can be used, a common running example is provided. Besides this, a set of desirable features that languages should exhibit to prove useful in engineering a MAS have been identified. A comparison of the six languages with respect to the support given to these features is provided, as well as final considerations on the usefulness of logic-based languages for "agent oriented software engineering".

Journal of Applied Logic, 2007

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 hardly 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, the programming language 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, the main contribution of this paper, rather than the language GOAL itself, is that 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.

Frontiers of Combining Systems, 2009

We discuss a new concept of agent programs that combines logic programming with reasoning about actions. These agent logic programs are characterized by a clear separation between the specification of the agent's strategic behavior and the underlying theory about the agent's actions and their effects. This makes it a generic, declarative agent programming language, which can be combined with an action representation formalism of one's choice. We present a declarative semantics for agent logic programs along with (two versions of) a sound and complete operational semantics, which combines the standard inference mechanisms for (constraint) logic programs with reasoning about actions.

Lecture Notes in Computer Science, 2010

In this paper we present an agent language that combines agent functionality with an action theory and model-theoretic semantics. The language is based on abductive logic programming (ALP), but employs a simplified state-free syntax, with an operational semantics that uses destructive assignment to manipulate a database, which represents the current state of the environment. The language builds upon the ALP combination of logic programs, to represent an agent's beliefs, and integrity constraints, to represent the agent's goals. Logic programs are used to define macro-actions, intensional predicates, and plans to reduce goals to sub-goals including actions. Integrity constraints are used to represent reactive rules, which are triggered by the current state of the database and recent agent actions and external events. The execution of actions and the assimilation of observations generate a sequence of database states. In the case of the successful solution of all goals, this sequence, taken as a whole, determines a model that makes the agent's goals and beliefs all true.

Lecture Notes in Computer Science, 2000

The notion of agents has provided a way of imbuing traditional computing systems with an extra degree of flexibility that allows them to be more resilient and robust in the face of more varied and unpredictable forms of interaction. One class of agents, typically called intelligent agents, represent their world symbolically according to their beliefs, have goals which need to be achieved, and adopt plans or intentions to achieve them. Now, one approach to building agents is to design a programming language whose semantics are based on some theory of rational or intentional agency and to program the desired behaviour of individual agents directly using mental attitudes. Such a technique is referred to as agent oriented programming. Arguably, the most innovative of these languages is 3APL (pronounced "triple-a-p-l") which supports the construction of intelligent agents for the development of complex systems through a set of intuitive concepts like beliefs, goals and plans. In this paper, we provide a Z specification of the programming language 3APL which provides a basis for implementation and also adds to a growing library of agent techniques and features.

Autonomous Agents and Multi-Agent Systems, 2008

Lecture Notes in Computer Science, 2007

In this paper we develop a semantics of our approach based on commitments and arguments for conversational agents. We propose a logical model based on CTL* (Extended Computation Tree Logic) and on dynamic logic. Called Commitment and Argument Network (CAN), our formal framework based on this hybrid approach uses three basic elements: social commitments, actions that agents apply to these commitments and arguments that agents use to support their actions. The advantage of this logical model is to gather all these elements and the existing relations between them within the same framework. The semantics we develop here enables us to reflect the dynamics of agent communication. It also allows us to establish the important link between commitments as a deontic concept and arguments. On the one hand CTL* enables us to express all the temporal aspects related to the handling of commitments and arguments. On the other hand, dynamic logic enables us to capture the actions that agents are committed to achieve.

2007

Research on agent communication languages has typically taken the speech acts paradigm as its starting point. Despite their manifest attractions, speech-act models of communication have several serious disadvantages as a foundation for communication in artificial agent systems. In particular, it has proved to be extremely difficult to give a satisfactory semantics to speech-act based agent communication languages. In part, the problem is that speech-act semantics typically make reference to the "mental states" of agents (their beliefs, desires, and intentions), and there is in general no way to attribute such attitudes to arbitrary computational agents. In addition, agent programming languages have only had their semantics formalised for abstract, stand-alone versions, neglecting aspects such as communication primitives. With respect to communication, implemented agent programming languages have tended to be rather ad hoc. This paper addresses both of these problems, by giving semantics to speech-act based messages received by an AgentSpeak agent. AgentSpeak is a logic-based agent programming language which incorporates the main features of the PRS model of reactive planning systems. The paper builds upon a structural operational semantics to AgentSpeak that we developed in previous work. The main contributions of this paper are as follows: an extension of our earlier work on the theoretical foundations of AgentSpeak interpreters; a computationally grounded semantics for (the core) performatives used in speech-act based agent communication languages; and a well-defined extension of AgentSpeak that supports agent communication.

Lecture Notes in Computer Science, 2001

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.

We propose a variant of Alternating-time Temporal Logic (ATL) grounded in the agents' operational know-how, as defined by their libraries of abstract plans. In our logic, it is possible to refer to "rational" strategies for agents developed under the Belief-Desire-Intention agent paradigm. This allows us to express and verify properties of BDI systems using ATL-type logical frameworks.