Strips-like Planning in the DALI Logic Programmming Language

2005

We discuss some features of the new logic programming language DALI for agents and multi-agent systems, also in connection to the issues raised in [12]. We focus in particular on the treatment of proactivity, which is based on the novel mechanism of the internal events and goals. As a case-study, we discuss the design and implementation of an agent capable to perform simple forms of planning. We demonstrate how it is possible in DALI to perform STRIPS-like planning without implementing a meta-interpreter.

Lecture Notes in Computer Science, 2004

We acknowledge support by the Information Society Technologies programme of the European Commission, Future and Emerging Technologies under the IST-2001-37004 WASP project.

2008

Abstract Many interesting architectures for defining intelligent agents have been proposed in the last years. Logic-based architectures have proved effective for reproducing “intelligent” behavior while staying within a rigorous formal setting. In this paper, we present the DALI multi-agent architecture, a logic framework for defining intelligent agents and multiagent systems.

DALI is a logic programming agent-oriented language defined in [1,2,3,4], fully formalized in [5,6]. DALI is fully implemented, and has been used in practice in a variety of applications [7,8,9,10]. A stable release of the DALI interpreter is publicly available at [11]. For the definition of DALI we have built under many respects upon our past work about meta-reasoning and reflection in logic programming languages [12,13,14,15,16]. In this work in particular, issues related to meta-level representation of predicates, atoms and rules are discussed in depth.

2006

This paper provides a general mechanism and a solid theoretical basis for performing planning within Belief-Desire-Intention (BDI) agents. BDI agent systems have emerged as one of the most widely used approaches to implementing intelligent behaviour in complex dynamic domains, in addition to which they have a strong theoretical background. However, these systems either do not include any built-in capacity for "lookahead" type of planning or they do it only at the implementation level without any precise defined semantics. In some situations, the ability to plan ahead is clearly desirable or even mandatory for ensuring success. Also, a precise definition of how planning can be integrated into a BDI system is highly desirable. By building on the underlying similarities between BDI systems and Hierarchical Task Network (HTN) planners, we present a formal semantics for a BDI agent programming language which cleanly incorporates HTN-style planning as a built-in feature. We argue that the resulting integrated agent programming language combines the advantages of both BDI agent systems and hierarchical offline planners.

Lecture Notes in Computer Science, 2014

Automated planning has been the subject of intensive research and is at the core of several areas of AI, including intelligent agents and robotics. In this paper, we argue that Transaction Logic is a natural specification language for planning algorithms, which enables one to see further afield and thus discover better and more general solutions than using one-of-a-kind formalisms. Specifically, we take the well-known STRIPS planning strategy and show that Transaction Logic lets one specify the STRIPS planning algorithm easily and concisely, and to prove its completeness. Moreover, extensions to allow indirect effects and to support action ramifications come almost for free. Finally, the compact and clear logical formulation of the algorithm made possible by this logic is conducive to fruitful experimentation. To illustrate this, we show that a rather simple modification of the STRIPS planning strategy is also complete and yields speedups of orders of magnitude.

IGI Global eBooks, 2011

This chapter introduces planning and knowledge representation in the declarative action language K. Rooted in the area of Knowledge Representation & Reasoning, action languages like K allow to formalize complex planning problems involving non-determinism and incomplete knowledge in a very flexible manner. By giving an overview of existing planning languages and comparing these against our language, we aim on further promoting the applicability and usefulness of high-level action languages in the area of planning. As opposed to previously existing languages for modeling actions and change, K adopts a logic programming view where fluents representing the epistemic state of an agent might be true, false or undefined in each state. We will show that this view of knowledge states can be fruitfully applied to several well-known planning domains from the literature as well as novel planning domains. Remarkably, K often allows to model problems more concisely than previous action languages. All the examples given can be tested in an available implementation, the DLV K planning system.

Woa, 2005

In this paper we introduce a form of cooperation among agents based on exchanging sets of rules. In principle, the approach extends to agent societies a feature which is proper of human societies, i.e., the cultural transmission of abilities. However, acquiring knowledge from untrustworthy agents should be avoided, and the new knowledge should be evaluated according to its usefulness. After discussing the general principles of our approach, we present a prototypical implementation. gered as if it were an external one. A DALI agent is able to build a plan in order to reach an objective, by using internal events of a particular kind, called planning goals. Actions are the agent's way of affecting the environment, possibly in reaction to either an external or internal event. An action in DALI can be also a message sent by an agent to another one. Definition 4 (Action): An action is syntactically indicated by postfix A: Action ::= << Atom A >> |message A << Atom, Atom >> Actions take place in the body of rules. If an action has preconditions, they are defined by action rules, emphasized by a new token: Definition 5 (Action rule): An action rule has the form: Action :< P reconditions. Similarly to external and internal events, actions are recorded as past actions. Past events represent the agent's "memory", that makes it capable to perform future activities while having experience of previous events, and of its own previous conclusions. Past events are kept for a certain default amount of time, that can be modified by the user through a suitable directive in the initialization file. A past event is syntactically indicated by the postfix P. Procedurally, DALI is based on an Extended Resolution Procedure that interleaves different activities, and can be tuned by the user via directives. The operational semantics of DALI is based on Dialogue Games Theory [4] [20]: the DALI Interpreter is modeled as a set of cooperating players. By means of this approach one is able to prove formal properies of the language in the form of properties that the game will necessarily fulfil. A. DALI Communication Architecture The DALI communication architecture consists of four levels. The first and last levels implement the DALI/FIPA communication protocol and a filter on communication, i.e. a set of rules that decide whether or not receive (told check level) or send a message (tell check level). The DALI communication filter is specified by means of meta-level rules defining the distinguished predicates tell and told. Whenever a message is received, with content part primitive(Content,Sender) the DALI interpreter automatically looks for a corresponding told rule. If such a rule is found, the interpreter attempts to prove told(Sender, primitive(Content)). If this goal succeeds, then the message is accepted, and primitive(Content)) is added to the set of the external events incoming into the receiver agent. Otherwise, the message is discarded. Symmetrically, the messages that an agent sends are subjected to a check via tell rules. The second level includes a metareasoning layer, that tries to understand message contents, possibly based on ontologies and/or on forms of commonsense reasoning. The third level consists of the DALI interpreter.

This paper stems from an experience made by Annalisa D&#x27;Andrea (with her colleague Daniela Pavone) as a student of the&#x27;Artificial Intelligence and Intelligent Agents&#x27; graduate course at the University of L&#x27;Aquila (held by Prof. Stefania Costantini and Dr. Arianna Tocchio). The experience has been further developed by Annalisa as a Ph. D. student, with her collegue Niva Florio and with the help of Dr. Giovanni De Gasperis. The application that we illustrate here is developed in DALI, an agent-oriented logical language that extends ...

This paper describes a new development related to the DALI logic agent-oriented programming language/framework, and discusses a case-study. In particular, DALI agents have been equipped with ASP (Answer Set programming) modules, which allow for affordable and flexible planning capabilities, and with the possibility to select plans according to a suite of possible preferences. The case-study concerns a DALI MAS (Multi-Agent System) whose composing agents cooperate for achieving the task of exploring an unknown territory.