Tina Balke

Norms in MAS: Definitions and Related Concepts

In this chapter we provide an introductory presentation of normative multi-agent systems (nMAS). The key idea of the chapter is that any definition of nMAS should preliminarily clarify meaning, scope, and function of the concept of norm. On account of this idea, we focus on three definitions and some related requirements for nMAS. For each of such definitions we propose some guidelines for developing nMAS. Second, we suggest how to relate the concept of nMAS to different conceptions of norms and how norms can be used within the systems. Finally, we identify some specific issues that open research questions or that exhibit interesting overlaps with other disciplines.

A model-based approach to the automatic revision of secondary legislation

Conflicts between laws can readily arise in situations governed by different laws, a case in point being when the context of an inferior law (or set of regulations) is altered through revision of a superior law. Being able to detect these conflicts automatically and resolve them, for example by proposing revisions to one of the modelled laws or policies, would be highly beneficial for legislators, legal departments of organizations or anybody having to incorporate legal requirements into their own procedures. In this paper we present a model based approach for detecting and finding legal conflicts through a combination of a formal model of legal specifications and a computational model based on answer set programming and inductive logic programming. Given specific scenarios (descriptions of courses of action), our model-based approach can automatically detect whether these scenarios could lead to contradictory outcomes in the different legal specifications. Using these conflicts as use cases, we apply inductive logic programming (ILP) to learn revisions to the legal component that is the source of the conflict. We illustrate our approach using a case-study where a university has to change its studentship programme after the government brings in new immigration regulations.

I-ABM: combining institutional frameworks and agent-based modelling for the design of enforcement policies

Computer science advocates institutional frameworks as an effective tool for modelling policies and reasoning about their interplay. In practice, the rules or policies, of which the institutional framework consists, are often specified using a formal language, which allows for the full verification and validation of the framework (e.g. the consistency of policies) and the interplay between the policies and actors (e.g. violations). However, when modelling large-scale realistic systems, with numerous decision-making entities, scalability and complexity issues arise making it possible only to verify certain portions of the problem without reducing the scale. In the social sciences, agent-based modelling is a popular tool for analysing how entities interact within a system and react to the system properties. Agent-based modelling allows the specification of complex decision-making entities and experimentation with large numbers of different parameter sets for these entities in order to explore their effects on overall system performance. In this paper we describe how to achieve the best of both worlds, namely verification of a formal specification combined with the testing of large-scale systems with numerous different actor configurations. Hence, we offer an approach that allows for reasoning about policies, policy making and their consequences on a more comprehensive level than has been possible to date. We present the institutional agent-based model methodology to combine institutional frameworks with agent-based simulations). We furthermore present J-InstAL, a prototypical implementation of this methodology using the InstAL institutional framework whose specifications can be translated into a computational model under the answer set semantics, and an agent-based simulation based on the jason tool. Using a simplified contract enforcement example, we demonstrate the functionalities of this prototype and show how it can help to assess an appropriate fine level in case of contract violations.

Analysing energy-incentivized cooperation in next generation mobile networks using normative frameworks and an agent-based simulation

Wireless mobile grids (WMG) have been proposed as the next generation mobile networks in order to address the energy issues arising for the next generation of mobile phones. WMG are based on the notion that local communication is more energy-efficient than the standard 3G communication. Despite their energy advantages, they create a social dilemma as it is advantageous for rational users to benefit from the energy savings without any contribution to the cooperation, as every commitment has its price. This paper proposes the use of a normative framework modelling technique and multi-agent simulations to support the early and rapid development of prototype systems to analyse solutions for solving the collaboration dilemma in WMG. Both tools allow for the capture of essential features of interactions between components in open architectures, therefore assisting in concept refinement, identification of actors, policy exploration and the feasibility assessment of new systems. With the help of these models we show how it is possible to quantify energy consumption, explore management policies and evaluate individual utility functions, all of which act as drivers in helping realise the WMG concept.

Normative Run-Time Reasoning for Institutionally-Situated BDI Agents

Institutions offer the promise of a means to govern open systems, in particular open multi-agent systems. Research in logics, and subsequently tools, supports the specification, verification and enactment of institutions. Most effort to date has focussed on the design-time properties of institutions (either on the normative or the system level), such as whether a particular state of affairs is reachable or not from a given set of initial conditions. Such models are useful in forcing the designer to state their intentions precisely, and for testing (design) properties. However, we identify two problems in the direct utilization of event-based design-time models in the governance of live (running) systems: (i) over-specification of constraints on agent autonomy and (ii) generation of design-time model artefacts. In this paper we present a methodology to tackle these two problems and extract the run-time model from the design-time one. We demonstrate how to derive an event-based run-time model of institutions that can be incorporated into the reasoning processes of autonomous BDI agents to realize practical norm-governed multi-agent systems.

Evaluating the Cost of Enforcement by Agent-Based Simulation: A Wireless Mobile Grid Example

The subject of this paper is the cost of enforcement, to which we take a satisficing approach through the examination of marginal cost-benefit ratios. Social simulation is used to establish that less enforcement can be beneficial overall in economic terms, depending on the costs to system and/or stakeholders arising from enforcement. The results are demonstrated by means of a case study of wireless mobile grids (WMGs). In such systems the dominant strategy for economically rational users is to free-ride, i.e. to benefit from the system without contributing to it. We examine the use of enforcement agents that police the system and punish users that take but do not give. The agent-based simulation shows that a certain proportion of enforcement agents increases cooperation in WMG architectures. The novelty of the results lies in our empirical evidence for the diminishing marginal utility of enforcement agents: that is how much defection they can foreclose at what cost. We show that an increase in the number of enforcement agents does not always increase the overall benefits-cost ratio, but that with respect to satisficing, a minimum proportion of enforcement agents can be identified that yields the best results.

The Uses of Norms

This chapter presents a variety of applications of norms. These applications include governance in sociotechnical systems, data licensing and data collection, understanding software development teams, requirements engineering, assurance, natural resource allocation, wireless grids, autonomous vehicles, serious games, and virtual worlds.

Detecting conflicts in legal systems

When acting in different jurisdictions (e.g. under the laws of different countries) at the same time, it can be of great value for individuals to be able to determine whether disparities among the laws of these different systems exist and allowing them to identify the consequences that may follow from these disparities. For individuals, it is typically not of interest to find all the ways in which these legal systems differ, but rather to establish whether a particular course of action may have different legal interpretations, depending on the jurisdiction. In this paper we present a formal and computational framework that, given specific scenarios (descriptions of courses of action), can automatically detect whether these scenarios could lead to different outcomes. We demonstrate our approach by means of a private international law case-study where a company drafts a contract clause after examining the consequences in the available jurisdictions.

Legal conflict detection in interacting legal systems

Acting under several jurisdictions at the same time is becoming the norm rather than the exception, certainly for companies but also (sometimes without knowing) for individuals. In these circumstances disparities among the different laws are inevitable. Here, we present a mathematical and a computational model of interacting legal specifications, along with a mechanism to find conflicts between them. We illustrate the approach by a case study using European Privacy law.

Simulation and NorMAS

In this chapter, we discuss state of the art and future perspective of the study of norms with simulative methodologies, in particular employing agent-based simulation. After presenting the state of the art and framing the simulative research on norms in a norm life-cycle schema, we list those research challenges that we feel more apt to be tackled by the simulative approach. We conclude the chapter with the indications for the realization of a NorMAS simulation platform, illustrated by selected scenarios.