Davide Grossi

Normative Multi-agent Programs and Their Logics

Multi-agent systems are viewed as consisting of individual agents whose behaviors are regulated by an organization artefact. This paper presents a simplified version of a programming language that is designed to implement norm-based artefacts. Such artefacts are specified in terms of norms being enforced by monitoring, regimenting and sanctioning mechanisms. The syntax and operational semantics of the programming language are introduced and discussed. A logic is presented that can be used to specify and verify properties of programs developed in this language.

Ubi Lex, Ibi Poena: Designing Norm Enforcement in E-Institutions

The viability of the application of the e-Institution paradigm for obtaining overall desired behavior in open multiagent systems (MAS) lies in the possibility of bringing the norms of the institution to have an actual impact on the MAS. Institutional norms have to be implementedin the society. The paper addresses two possible views on implementing norms, the so-called regimentationof norms, and the enforcementof norms, with particular attention to this last one. Aim of the paper is to provide a theory for the understanding of the notion of enforcement and for the design of enforcement mechanisms in e-Institutions.

Organizational structure and responsibility: an analysis in a dynamic logic of organized collective agency

Aim of the present paper is to provide a formal characterization of various different notions of responsibility within groups of agents (Who did that? Who gets the blame? Who is accountable for that? etc.). To pursue this aim, the papers proposes an organic analysis of organized collective agency by tackling the issues of organizational structure, role enactment, organizational activities, task-division and task-allocation. The result consists in a semantic framework based on dynamic logic in which all these concepts can be represented and in which various notions of responsibility find a formalization. The background motivation of the work consists in those responsibility-related issues which are of particular interest for the theory and development of multi-agent systems.

Foundations of organizational structures in multiagent systems

We analyze the notion of organizational structure in multiagent systems and explain the precise added value and the effects of such organizational structure on the involved agents. To pursue this aim, contributions from social and organization theory are considered which provide a solid theoretical foundation to this analysis. We argue that organizational structures should be seen along at least three dimensions, instead of just one: power, coordination, and control. In order to systematize the approach, formal tools are used to describe the organizational structure as well as the effect of such structures on the activities in multiagent systems. We specify the properties and the consequences of organizational structures for the actions of the involved agents.

Judgment Aggregation: A Primer

Judgment aggregation is a mathematical theory of collective decision-making. It concerns the methods whereby individual opinions about logically interconnected issues of interest can, or cannot, be aggregated into one collective stance. Aggregation problems have traditionally been of interest for disciplines like economics and the political sciences, as well as philosophy, where judgment aggregation itself originates from, but have recently captured the attention of disciplines like computer science, artificial intelligence and multi-agent systems. Judgment aggregation has emerged in the last decade as a unifying paradigm for the formalization and understanding of aggregation problems. Still, no comprehensive presentation of the theory is available to date. This Synthesis Lecture aims at filling this gap presenting the key motivations, results, abstractions and techniques underpinning it.

Classificatory Aspects of Counts-as

The article investigates the logic underlying statements of the form ‘X counts as Y in context C’ which are commonly considered to represent the paradigmatic syntax of constitutive rules, i.e. the non-regulative component of normative systems. The analytical thesis backing the whole work consists in interpreting such statements as contextual classifications. This reading of counts-as is thoroughly investigated in two variants which we call the contextual classificatory reading and the proper contextual classificatory reading. The formal analysis of these readings, which we carry out making use of modal logic, disentangles two possible senses in which counts-as statements can be interpreted within a classificatory perspective, and clarifies the logical relations holding between them. The proposal is then compared in detail with previous work on the topic, in order to shed light on similarities, differences and their grounds.

Collective Obligations and Agents: Who Gets the Blame?

This work addresses the issue of obligations directed to groups of agents. Our main concern consists in providing a formal analysis of the structure connecting collective obligations to individual ones: which individual agent in a group should be held responsible if an obligation directed to the whole group is not fulfilled? To this aim, concepts from planning literature (like plan and task allocation) are first used in order to conceptualize collective agency, and then formalized by means of a dynamic deontic logic framework. Within this setting, a formal account of the notion of coordination, intended as management of interdependencies among agents’ activities, is also provided.

The many faces of counts-as: A formal analysis of constitutive rules

Abstract The paper proposes a logical systematization of the notion of counts-as which is grounded on a very simple intuition about what counts-as statements actually mean, i.e., forms of classification. Moving from this analytical thesis the paper disentangles three semantically different readings of statements of the type “X counts as Y in context c”, from the weaker notion of contextual classification to the stronger notion of constitutive rule. These many ways in which counts-as can be said are formally addressed by making use of modal logic techniques. The resulting framework allows for a formal characterization of all the involved notions and their reciprocal logical relationships.

Contextual taxonomies

We provide a formal characterization of a notion of contextual taxonomy, that is to say, a taxonomy holding only with respect to a specific context. To this aim, a new proposal for dealing with “contexts as abstract mathematical entities” is set forth, which is geared toward solving some problems arising in the area of normative system specifications for modeling multi-agent systems. Contexts are interpreted as sets of description logic models for different languages, and a number of operations on contexts are defined. Using this framework, a simple scenario taken from the legal domain is modeled, and a formal account of the so called open-texture of legal terms is provided characterizing the notions of “core” and “penumbra” of the meaning of a concept.

Twelve angry men: a study on the fine-grain of announcements

By moving from a suggestive example, the paper analyzes how information flows among agents involved in a deliberation. By deliberating, agents become aware of details, draw the attention of the group to some issues, perform inferences and announce what they know. The proposed framework--which builds on the paradigm of dynamic logic-- captures how, during a deliberation, information results from stepwise multi-agent interaction.