The Logic Behind Negotiation: From Pre-Argument Reasoning to Argument-Based Negotiation

The use of agents in Electronic Commerce environments leads to the necessity to introduce some formal analysis and definitions. A four-step method is introduced for developing EC-directed agents, which are able to take into account nonlinearites such as gratitude and agreement. Negotiations that take into account a multistep exchange of arguments provide extra information, at each step, for the intervening agents, enabling them to react accordingly. This argument-based negotiation among 701 E. Chocolate Avenue, Hershey PA 17033-1240, USA Tel: 717/533-8845; Fax 717/533-8661; URL-http://www.idea-group.com ITB8746 IDEA GROUP PUBLISHING This chapter appears in the book, Intelligent Agent Software Engineering, edited by Valentina Plekhanova. Copyright © 2003, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. is prohibited. 138 Brito, Novais & Neves Copyright © 2003, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. is prohibited. Copy right Idea Grou p Inc . Copy right Idea Grou p Inc . opyri ght Id ea G roup Inc. Copy right Idea Grou p Inc . agents has much to gain from the use of Extended Logic Programming mechanisms. Incomplete information is common in EC scenarios; therefore, arguments must also take into account the presence of statements with an unknown valuation. INTRODUCTION The amount of ambiguity present in real-life negotiations is intolerable for automatic reasoning systems. Concepts present in each intervening party of a real-life negotiation need to be objectively formalized in order for an automatic approach to be reached. Logic, and especially, Extend Logic Programming (ELP) (Baral & Gelfond, 1994) poses itself as a powerful tool to achieve the desired formality without compromising comprehension and readability, and the ability to easily build an executable prototype for agents. Logical formulas are extremely powerful, unambiguous, and possess a set of interesting advantages (McCarthy, 1959): Expressing information in declarative sentences is far more modular than expressing it in segments of computer programs or in tables. Sentences can be true in a much wider context than specific programs can be used. The supplier of a fact does not have to understand much about how the receiver functions or how or whether the receiver will use it. The same fact can be used for many purposes, because the logical consequences of collections of facts can be available. However, in a dynamic environment such as the one found in electronic commerce (EC), the simple use of logical formulas is not enough. The use of nonmonotonic characteristics is self-evident (which is in some way found in ELP) (Neves, 1984). In general logic programs, negative information is provided by the closedworld assumption (i.e., everything that cannot be proven to be true is false), however, in extended logic programs, that is not so. In ELP, a query may fail due to the fact that information is not available to support it or, on the other hand, it may fail due to the fact that negation succeeds. The knowledge base (KB), which serves as the basis for the agent’s reasoning, can be seen has an extended logic program (P) that is a collection f rules with the form: L0 ← L1, ..., Lm, not Lm+1, ..., not Ln 21 more pages are available in the full version of this document, which may be purchased using the "Add to Cart" button on the publisher's webpage: www.igi-global.com/chapter/logic-behind-negotiation/24148