Dynamic Specifications for Norm-Governed Systems

Dynamic Specifications for Norm-Governed Systems

Alexander Artikis (National Centre for Scientific Research “Demokritos”, Greece), Dimosthenis Kaponis (Imperial College London, UK) and Jeremy Pitt (Imperial College London, UK)
DOI: 10.4018/978-1-60566-256-5.ch019
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Abstract

We have been developing a framework for executable specification of norm-governed multi-agent systems. In this framework, specification is a design-time activity; moreover, there is no support for run-time modification of the specification. Due to environmental, social, or other conditions, however, it is often desirable, or even necessary, to alter the system specification during the system execution. In this chapter we extend our framework by allowing for “dynamic specifications”, that is, specifications that may be modified at run-time by the members of a system. The framework extension is motivated by Brewka’s “dynamic argument systems”—argument systems in which the rules of order may become the topic of the debate. We illustrate our framework for dynamic specifications by presenting: (i) a dynamic specification of an argumentation protocol, and (ii) an execution of this protocol in which the participating agents modify the protocol specification.
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Introduction

A particular kind of Multi-Agent System (MAS) is one where the member agents are developed by different parties, and where there is no direct access to an agent’s internal state. In this kind of MAS it cannot be assumed that all agents will behave according to the system specification because the agents act on behalf of parties with competing interests, and thus they may inadvertently fail to, or even deliberately choose not to, conform to the system specification in order to achieve their individual goals. A few examples of this type of MAS are Virtual Organisations, electronic marketplaces, argumentation (dispute resolution) protocols, and negotiation protocols. MAS of this type are often classified as ‘open’.

We have been developing executable specifications of open MAS (Artikis, 2003; Artikis, Sergot & Pitt, 2003; 2007); we adopt a bird’s eye view of these systems, as opposed to an agent’s own perspective whereby it reasons about how it should act. Furthermore, we view agent systems as instances of normative systems (Jones & Sergot, 1993). A feature of this type of system is that actuality, what is the case, and ideality, what ought to be the case, do not necessarily coincide. Therefore, it is essential to specify what is permitted, prohibited, and obligatory, and perhaps other more complex normative relations that may exist between the agents. Amongst these relations, we place considerable emphasis on the representation of institutionalised power (Jones & Sergot, 1996) — a standard feature of any norm-governed system whereby designated agents, when acting in specified roles, are empowered by an institution to create specific relations or states of affairs (such as when an agent is empowered by an institution to award a contract and thereby create a bundle of normative relations between the contracting parties). We encode specifications of open MAS in executable action languages from the field of Artificial Intelligence (Giunchiglia, Lee, Lifschitz, McCain & Turner, 2004; Kowalski & Sergot, 1986).

Our executable specifications may be classified as ‘static’, in the sense that there is no support for their run-time modification. In some open MAS, however, environmental, social or other conditions may favour, or even require, specifications modifiable during the system execution. Consider, for instance, the case of a malfunction of a large number of sensors in a sensor network, or the case of manipulation of a voting procedure due to strategic voting, or when an organisation conducts its business in an inefficient manner. Therefore, we present in this chapter an infrastructure for ‘dynamic specifications’, that is, specifications that are developed at design-time but may be modified at run-time by the members of a system. The presented infrastructure is motivated by Brewka’s ‘dynamic argument systems’ (Brewka, 2001) — argument systems in which, at any point in the disputation, participants may start a meta level debate, that is, the rules of order can become the current point of discussion, with the intention of altering these rules.

Our infrastructure for dynamic specifications allows protocol participants to alter the rules of a protocol P during the protocol execution. P is considered an ‘object’ protocol; at any point in time during the execution of the object protocol the participants may start a ‘meta’ protocol in order to decide whether the object protocol rules should be modified: add a new rule-set, delete an existing one, or replace an existing rule-set with a new one. Moreover, the participants of the meta protocol may initiate a meta-meta protocol to decide whether to modify the rules of the meta protocol, or they may initiate a meta-meta-meta protocol to modify the rules of the meta-meta protocol, and so on.

Key Terms in this Chapter

Hierarchical Structure: A pyramid-shaped system that arranges the relations between the entities within an organization in a top-down way. Power, responsibility and authority are concentrated at the top of the pyramid and decisions flow from the top downwards. The pyramid can be more steep or more flat. A steep pyramid has many layers of management, a flat organization has relatively few (Companion to Organizations, J. Baum, 2002).

Organizational Performance: Comprises the actual output or results of an organization as measured against its intended outputs (or goals and objectives). It is a broad construct which captures what organizations do, produce, and accomplish for the various constituencies with which they interact. Specialists in many fields are concerned with organizational performance including strategic planners, operations, finance, legal, and organizational development (Companion to Organizations, J. Baum Eds., Oxford Blackwell, UK, 2002).

Generative Interactions: Interactions are generative to the extent that they allow for the emergence of new capabilities to handle complexity, notably the increased complexity of signals from the environment. They are used to gain additional knowledge and insight. The value of interactions is rising because their generative function has become the solution to increasingly challenging organizational problems that go far beyond coordination needs (Morieux et al, 2005).

Routines: In the economics and business literatures, the notion of organizational routine has come to stand for regularity in economic activity. The concept of organizational routine is used to capture repetitive, stable activity leading to behavior patterns or recurrent interaction patterns. However the term is used also refering to some cognitive representation such as rules and cognitive. “We will regard a set of activities as routinized, [then,] to the degree that choice has been simplified by the development of a fixed response to defined stimuli. If search has been eliminated, but a choice remains in the form of clearly defined and systematic computing routine, we will say that the activities are routinized” (March and Simon 1993, page 142).

Bounded Rationality: A term for the phenomenon that cognitive blinders prevent people from seeing, seeking, using, or sharing relevant, accessible, and perceivable information during decision-making. The bounded rationality phenomenon challenges traditional rationalist perspectives and suggests that the rationality of actual human and company behavior is always partial, or ‘bounded’ by human limitations. This concept recognizes that decision making takes place within an environment of incomplete information and uncertainty. Herbert Simon pointed out that most people are only partly rational, and are in fact emotional and irrational in the remaining part of their actions. They experience limits in formulating and solving complex problems and in processing (receiving, storing, retrieving, transmitting) information (Companion to Organizations, J. Baum Eds., Oxford Blackwell, UK, 2002).

Span of Control: Refers to how relationships are structured between leaders and subordinates in organizations. It represents the number of people/subordinates that can be effectively managed by one manager. The optimal Span of Control is dependent upon the nature of the work of the subordinates, the skills, capabilities, experience, seniority, qualifications of the managers and subordinates, the use of information technology, the detail at which work rules and procedures have been formalized and are known by the subordinates, the applied management style and the desired depth of the hierarchy in an organization (Companion to Organizations, J. Baum Eds., Oxford Blackwell, UK, 2002).

Satisficing: In economics, satisficing is a behavior which attempts to achieve at least some minimum level of a particular variable, but which does not necessarily maximize its value. The most common application of the concept in economics is in the behavioural theory of the firm, which, unlike traditional accounts, postulates that producers treat profit not as a goal to be maximized, but as a constraint. Under these theories, a critical level of profit must be achieved by firms; thereafter, priority is attached to the attainment of other goals. The word satisfice was coined by Herbert Simon as a portmanteau of “satisfy” and “suffice”. Simon pointed out that human beings lack the cognitive resources to maximize: we usually do not know the relevant probabilities of outcomes, we can rarely evaluate all outcomes with sufficient precision, and our memories are weak and unreliable.

Allocative Interactions: Are used to coordinate events, functions, businesses, etc. such that these fit together and fit with a pre-existing scheme while minimizing the time, energy, etc. consumed to ensure the fit (Morieux et al, 2005).

Near Decomposability: According to H. Simon basically all viable systems, be they physical, social, biological, artificial, share the property of having a near decomposable architecture: they are organized into hierarchical layers of parts, parts of parts, parts of parts of parts and so on, in such a way that interactions among elements belonging to the same parts are much more than interactions among elements belonging to different parts. By “intense” interaction is meant that the behavior of one component depends more closely on the behavior of other components belonging to the same part than on components belonging to other parts (i.e. the cross-derivatives are larger within a part). This kind of architecture can be found in business firms, where division of labor, divisionalization, hierarchical decomposition of tasks are all elements which define a near decomposable system: individuals within a hierarchical subunit have closer, more widespread, more intense and more frequent interactions than individuals belonging to different subunits. But a very similar architecture can also be found in most complex artifacts (which are made by assembling parts and components, which in turn can be assemblies of other parts and components, and so on), in software (with the use of subroutines, and even more so in object-oriented programming) (Egidi and Marengo, 2006).

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Editorial Advisory Board
Table of Contents
Foreword
Liz Sonenberg
Preface
Virginia Dignum
Acknowledgment
Virginia Dignum
Chapter 1
Virgina Dignum
Agent Organization can be understood from two perspectives: organization as a process and organization as an entity. That is, organization is... Sample PDF
The Role of Organization in Agent Systems
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Chapter 2
Luciano R. Coutinho, Jaime S. Sichman, Olivier Boissier
In this chapter, we discuss the concepts of agent organization, organizational model, and review some existing organizational models. Before the... Sample PDF
Modelling Dimensions for Agent Organizations
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Chapter 3
Jacques Ferber, Tiberiu Stratulat, John Tranier
In this chapter, we stress the importance of thinking a MAS in all its aspects (agents, environment, interactions, organizations, and institutions)... Sample PDF
Towards an Integral Approach of Organizations in Multi-Agent Systems
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Chapter 4
Scott A. DeLoach
This chapter introduces a suite of technologies for building complex, adaptive systems. It is based in the multi-agent systems paradigm and uses the... Sample PDF
OMACS: A Framework for Adaptive, Complex Systems
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Chapter 5
Christopher Cheong, Michael Winikoff
Although intelligent agents individually exhibit a number of characteristics, including social ability, flexibility, and robustness, which make them... Sample PDF
Hermes: Designing Flexible and Robust Agent Interactions
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Chapter 6
Viara Popova, Alexei Sharpanskykh
This chapter introduces a formal framework for modeling and analysis of organizations. It allows representing and reasoning about all important... Sample PDF
A Formal Framework for Organization Modeling and Analysis
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Chapter 7
Maksim Tsvetovat
Agent-based approaches provide an invaluable tool for building decentralized, distributed architectures and tying together sets of disparate... Sample PDF
Describing Agent Societies: A Declarative Semantics
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Chapter 8
Davide Grossi, Frank Dignum
In this chapter we investigate how organizations can be represented as graphs endowed with formal semantics. We distinguish different dimensions of... Sample PDF
Structural Aspects of Organizations
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Chapter 9
Virgina Dignum, Frank Dignum
Organization concepts and models are increasingly being adopted for the design and specification of multi-agent systems. Agent organizations can be... Sample PDF
A Logic for Agent Organizations
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Chapter 10
Cristiano Castelfranchi
This chapter presents organizations as a macro-micro notion and device; they presuppose autonomous proactive entities (agents) playing the... Sample PDF
Grounding Organizations in the Minds of the Agents
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Chapter 11
Paolo Torroni, Pinar Yolum, Munindar P. Singh, Marco Alberti, Federico Chesani, Marco Gavanelli, Evelina Lamma, Paola Mello
Organizational models often rely on two assumptions: openness and heterogeneity. This is, for instance, the case with organizations consisting of... Sample PDF
Modelling Interactions via Commitments and Expectations
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Chapter 12
Gita Sukthankar, Katia Sycara, Joseph A. Giampapa, Christopher Burnett
This chapter discusses the problem of agent aiding of ad-hoc, decentralized human teams so as to improve team performance on time-stressed group... Sample PDF
Communications for Agent-Based Human Team Support
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Chapter 13
Bob van der Vecht, Frank Dignum, John-Jules Ch. Meyer
This chapter discusses how autonomous agents can adopt organizational rules into their reasoning process. Agents in an organization need to... Sample PDF
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Chapter 14
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The specification of open interaction systems is widely recognized to be a crucial issue, which involves the problem of finding a standard way of... Sample PDF
Specifying Artificial Institutions in the Event Calculus
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Chapter 15
Francesco Viganò, Marco Colombetti
Institutions have been proposed to explicitly represent norms in open multi-agent systems, where agents may not follow them and which therefore... Sample PDF
Verifying Organizations Regulated by Institutions
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Chapter 16
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Chapter 17
Antônio Carlos da Rocha Costa, Graçaliz Pereira Dimuro
This chapter presents the Population-Organization model, a formal tool for studying the organization of open multi-agent systems and its functional... Sample PDF
A Minimal Dynamical MAS Organization Model
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Chapter 18
Shaheen Fatima, Michael Wooldridge
This chapter presents an adaptive organizational policy for multi-agent systems called TRACE. TRACE allows a collection of multi-agent organizations... Sample PDF
A Framework for Dynamic Agent Organizations
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Chapter 19
Alexander Artikis, Dimosthenis Kaponis, Jeremy Pitt
We have been developing a framework for executable specification of norm-governed multi-agent systems. In this framework, specification is a... Sample PDF
Dynamic Specifications for Norm-Governed Systems
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Chapter 20
Marco Lamieri, Diana Mangalagiu
In this chapter we present a model of organization aimed to understand the effect of formal and informal structures on the organization’s... Sample PDF
Interactions Between Formal and Informal Organizational Networks
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Chapter 21
Steven Okamoto, Katia Sycara, Paul Scerri
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Chapter 22
Sachin Kamboj, Keith S. Decker
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Chapter 23
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