A Convention-based Approach to Agent Communication Languages

Abstract

This article aims to provide foundations for a new approach to Agent Communication Languages (ACLs). First, we present the theory of signalling acts. In contrast to current approaches to communication, this account is neither intention-based nor commitment-based, but convention-based. Next, we explore ways of embedding that theory within an account of conversation. We move here from an account of the basic types of communicative act (the statics of communication) to an account of their role in sequences of exchanges in communicative interaction (the dynamics of communication). Finally, we apply the framework to the analysis of conversational protocols such as the English auction protocol. We propose to give a compact expression of conversation protocols by means of a formula of the object-language. We also use this kind of representation to provide the basis for a procedure for keeping a record of the conventional effects achieved in a conversation. A corresponding axiomatic presentation is given, and shown to be sound and complete with respect to our proposed semantics.

The normative aspect of signalling and the distinction between performative and constative

“…3 By 'communication system' we here mean the set of conventions that constitute the system, together with the set of agents who make use of those conventions. 4 It is irrelevant to the present point whether or not j believes that B does not hold. 5 One of the reviewers helpfully pointed out that this way of characterising the purpose of asserting strongly suggests an analysis of 'ought' along Andersonian lines, relating failure to violation.…”

“…And suppose further that agent j , who is an s-user, does A in circumstances in which B does not hold. 4 Then it is appropriate to say that, from the point of view of the institution s, something has gone wrong, in as much as the purpose or function within institution s of acts of asserting is to facilitate the transmission of reliable information. The point of asserting, as an institutionalised act, is to be able to show how things stand in a given state of affairs.…”

“…6 Following the theory developed in [3] and [4], the form of the signalling convention (sc) according to which, in s, agent j 's seeing to it that A counts as an assertion that B, is given by (sc-assert) E j A ⇒ s I * s B where expressions of the form E j A are read 'j sees to it that A', ⇒ s is the 'counts as' connective of [9], and I * s is a normative operator, intended to capture the sense of 'ought', or ideality, alluded to above. Details of the logics 2 This section offers merely a summary of the approach to signalling conventions described in [3] and [4], and the reader is referred to those sources-particularly to [4]-for a more detailed account, including details of the component modalities. The focus of the present paper is on the normative aspect of signalling conventions, and its relation to trust and to Austin's distinction between performative and constative.…”

Normative-informational positions: a modal-logical approach

“…In (Jones and Parent 2004;Jones and Parent 2007) modal-logical characterisations are given of the (forms of) conventions that constitute various key types of signalling acts: asserting, commanding, requesting,promising, ... among others. These characterisations employ several modalities, among them an ideality/ optimality modality, 'I H s ; , 3 used to represent those states of affairs that would obtain if a conventional signalling system were in an optimal state, relative to its function of facilitating the transmission of reliable information.…”

“…It was introduced in the multi-modal language described in(Jones and Parent 2007) merely to distinguish this particular notion of ideality from an evaluative normative modality, 'I', that also figured in the same language.…”