Julian Padget

AAMAS Conference 2023 Conference Paper

Agent-directed Runtime Norm Synthesis

• Andreasa Morris-Martin
• Marina De Vos
• Julian Padget
• Oliver Ray

To maintain fitness-for-purpose, the set of norms governing a MAS will typically need to evolve to reflect the changing needs of both participants and the environment. We put forward a conceptual framework to address this problem comprising dynamic institutions (sets of norms), that depend upon the formulation of new norms and the revision of existing norms, informed by the experiences of agents participating in the MAS. The objective is to allow participating agents to influence the revision of the norms governing the MAS, thereby taking a first step towards adaptable self-governance of socio-technical systems through explicit norms. This paper proposes a novel framework for revising at runtime the norms of a formally specified institution, directed by the agents in the MAS. The framework employs special-purpose synthesiser agents with partial observability of the state of the MAS to formulate new norms or revise existing ones, in response to requests from agents for changes to the institution. To demonstrate the feasibility of the framework, we capture a set of norms using the InstAL institutional specification language and revise those norms using the XHAIL symbolic machine learning system. Building freely on Sergot’s room scenario as a case study, we show how to synthesise norms that can resolve runtime institutional conflicts, and so establish the viability of a method for decentralised agent-directed runtime (online) revision of explicit norms.

TAAS Journal 2019 Journal Article

Argumentation-Based Reasoning about Plans, Maintenance Goals, and Norms

• Zohreh Shams
• Marina De Vos
• Nir Oren
• Julian Padget

In a normative environment, an agent’s actions are directed not only by its goals but also by the norms activated by its actions and those of other actors. The potential for conflict between agent goals and norms makes decision making challenging, in that it requires looking ahead to consider the longer-term consequences of which goal to satisfy or which norm to comply with in face of conflict. We therefore seek to determine the actions an agent should select at each point in time, taking account of its temporal goals, norms, and their conflicts. We propose a solution in which a normative planning problem is the basis for practical reasoning based on argumentation. Various types of conflict within goals, within norms, and between goals and norms are identified based on temporal properties of these entities. The properties of the best plan(s) with respect to goal achievement and norm compliance are mapped to arguments, followed by mapping their conflicts to attack between arguments, all of which are used to identify why a plan is justified.

JAAMAS Journal 2019 Journal Article

Norm emergence in multiagent systems: a viewpoint paper

• Andreasa Morris-Martin
• Marina De Vos
• Julian Padget

Abstract Norms are utilised in agent societies to encourage acceptable behaviour by the participating agents. They can be established or revised from the top-down (authority) or from the bottom-up (populace). The study of norm creation from the bottom-up—or norm emergence/convergence—shows evidence of increasing activity. In consequence, we seek to analyse and categorize the approaches proposed in the literature for facilitating norm emergence. This paper makes three contributions to the study of norm emergence. Firstly, we present the different perspectives of norms and their impact on the norm emergence process, with the aim of comparing their similarities and differences in implementing the norm life cycle. Secondly, we identify the characteristics that support norm emergence that are observed in the emergence literature. Finally, we identify and propose future topics for study for the community, through a discussion of the challenges and opportunities in norm emergence.

IJCAI Conference 2018 Conference Paper

Deontic Sensors

• Julian Padget
• Marina De Vos
• Charlie Ann Page

Normative capabilities in multi-agent systems (MAS) can be represented within agents, separately as institutions, or a blend of the two. This paper addresses how to extend the principles of open MAS to the provision of normative reasoning capabilities, which are currently either embedded in existing MAS platforms - tightly coupled and inaccessible - or not present. We use a resource-oriented architecture (ROA) pattern, that we call deontic sensors, to make normative reasoning part of an open MAS architecture. The pattern specifies how to loosely couple MAS and normative frameworks, such that each is agnostic of the other, while augmenting the brute facts that an agent perceives with institutional facts, that capture each institution's interpretation of an agent's action. In consequence, a MAS without normative capabilities can acquire them, and an embedded normative framework can be de-coupled and opened to other MAS platforms. More importantly, the deontic sensor pattern allows normative reasoning to be published as services, opening routes to certification and re-use, creation of (formalized) trust and non-specialist access to "on demand'' normative reasoning.

IS Journal 2017 Journal Article

Online Prediction via Continuous Artificial Prediction Markets

• Fatemeh Jahedpari
• Talal Rahwan
• Sattar Hashemi
• Tomasz P. Michalak
• Marina De Vos
• Julian Padget
• Wei Lee Woon

Prediction markets are well-established tools for aggregating information from diverse sources into accurate forecasts. Their success has been demonstrated in a wide range applications, including presidential campaigns, sporting events, and economic outcomes. Recently, they've been introduced to the machine learning community in the form of artificial prediction markets, in which algorithms trade contracts reflecting their levels of confidence. To date, these markets have mostly been studied in the context of offline classification, with promising results. The authors extend them to enable their use in online regression and introduce adaptive trading strategies informed by individual trading history and the ability of participants to revise their predictions by reflecting on the wisdom of the crowd, which is manifested in the collective performance of the market. The authors empirically evaluate their model using multiple datasets and show that it outperforms several well-established techniques from the literature on online regression.

EAAI Journal 2017 Journal Article

Practical reasoning with norms for autonomous software agents

• Zohreh Shams
• Marina De Vos
• Julian Padget
• Wamberto W. Vasconcelos

Autonomous software agents operating in dynamic environments need to constantly reason about actions in pursuit of their goals, while taking into consideration norms which might be imposed on those actions. Normative practical reasoning supports agents making decisions about what is best for them to (not) do in a given situation. What makes practical reasoning challenging is the interplay between goals that agents are pursuing and the norms that the agents are trying to uphold. We offer a formalisation to allow agents to plan for multiple goals and norms in the presence of durative actions that can be executed concurrently. We compare plans based on decision-theoretic notions (i. e. utility) such that the utility gain of goals and utility loss of norm violations are the basis for this comparison. The set of optimal plans consists of plans that maximise the overall utility, each of which can be chosen by the agent to execute. We provide an implementation of our proposal in Answer Set Programming, thus allowing us to state the original problem in terms of a logic program that can be queried for solutions with specific properties.

IJCAI Conference 2016 Conference Paper

Normative Practical Reasoning via Argumentation and Dialogue

• Zohreh Shams
• Marina De Vos
• Nir Oren
• Julian Padget

In a normative environment an agent's actions are not only directed by its goals but also by norms. Here, potential conflicts among the agent's goals and norms makes decision-making challenging. We therefore seek to answer the following questions: (i) how should an agent act in a normative environment? and (ii) how can the agent explain why it acted in a certain way? We propose a solution in which a normative planning problem serves as the basis for a practical reasoning approach based on argumentation. The properties of the best plan(s) w. r. t. goal achievement and norm compliance are mapped to arguments that are used to explain why a plan is justified, using a dialogue game.

AAMAS Conference 2013 Conference Paper

Governing Intelligent Virtual Agent Behaviour with Norms

• Jeehang Lee
• Tingting Li
• Marina De Vos
• Julian Padget

One requirement by which virtual environments (VEs) are judged, is the believability of the virtual agents (VAs). One aspect of believability, is that agent responses to situations should not create cognitive dissonance and thereby distract the observer. One approach to this problem is the use of institutional models providing social reasoning, in conjunction with classical AI techniques providing individual reasoning, to achieve the appropriate recognition of complex situations and provide guidance on the subsequent choice of action(s). We present a distributed approach that offers governance – rather than regimentation – of intelligent virtual agents (IVAs) situated in a VE. We aim to show that the combination of an institution providing social reasoning and BDI agents providing individual reasoning, establishes a framework for enhancing believability through the interplay between: (i) the institution and IVAs in VEs, and (ii) norms maintained by the institution and the mental states of IVAs. From an engineering point of view, the framework provides a separation of concerns because the BDI agent is augmented with the capacity to process social obligations, while the specification and verification of social structure resides in the institutional models.

AILAW Journal 2013 Journal Article

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

• Tina Balke
• Marina De Vos
• Julian Padget

Abstract 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-Inst AL, a prototypical implementation of this methodology using the Inst AL 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.

AAMAS Conference 2012 Conference Paper

Handling Change in Normative Specifications

• Duangtida Athakravi
• Domenico Corapi
• Alessandra Russo
• Marina De Vos
• Julian Padget
• Ken Satoh

Normative frameworks provide a means to address the governance of open systems, by offering a mechanism to express responsibilities and permissions of the individual participants with respect to the entire system without compromising their autonomy. Careful design is crucial if it is to meet its requirements. Tools that support the design process can be of great benefit. In this paper, we describe a method for choosing the appropriate change in the normative specification, using impact analysis of the critical consequences being preserved or rejected by the change.

AAMAS Conference 2011 Conference Paper

On-line Reasoning for Institutionally-Situated BDI agents

• Tina Balke
• Marina De Vos
• Julian Padget
• Dimitris Traskas

Institutions offer the promise of a means to govern open systems, in particular, open multi-agent systems. Research in logics and their derived tools now support the specification, verification and enactment of institutions (or organizations, depending on the terminology of the tool). Most effort to date has tended to focus on the static properties of institutions, 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 (static) properties. We call this off-line reasoning. We identify two problems in the direct utilization of off-line models in the governance of live systems: (i) static model artefacts that are typically aspects of agent behaviour in the dynamic model (ii) over-specification of constraints on actions, leading to undue limitation of agent autonomy. Agents need to be able to query an institution for (dynamic) properties. We call this on-line reasoning. In this paper we present a methodology to extract the on-line specification from an off-line one and use it to support BDI agents to realize a norm-governed multi-agent system.

IS Journal 2010 Journal Article

Adaptable, Organization-Aware, Service-Oriented Computing

• Huib Aldewereld
• Julian Padget
• Wamberto Vasconcelos
• Javier Vazquez-Salceda
• Paul Sergeant
• Athanasios Staikopoulos

Service-oriented computing is the new wave emerging from maturing Web services and the adoption of elements from Semantic Web technology. More sophistication, in response to business requirements, does of course not make it easier to use or to control. In particular, business processes demand resilience and real-time adaptation in the face of changing business requirements, incorporation of alternative services and finding suitable substitutes when those needed are unavailable. The European Union-funded Alive project is prototyping ideas, driven by commercial and industrial use cases, that utilize research in organizational modeling, software agents, model-driven engineering, artificial intelligence, the Semantic Web, and Web services to construct tools and demonstrators to address these needs. This article outlines the Alive architecture for service-oriented computing, describes some of the innovative tools we have developed and illustrates it all with a detailed run-through from one of our use cases.

AAMAS Conference 2010 Conference Paper

ALIVE: An Agent-Based Framework for Dynamic and Robust Service-Oriented Applications

• Javier Vazquez
• Wamberto W. Vasconcelos
• Julian Padget
• Frank Dignum
• Siobhan Clarke
• Manel Palau Roig

Service-oriented systems are becoming more and more nodes in adigital, dynamic ecosystem requiring the identification and establishment of flexible, spontaneous collaboration activities betweenservices. This requires new engineering approaches that can integrate new functionalities and behaviours into existing running systems of active, distributed and interdependent processes. Here, wepresent the approach of the FP7 ALIVE1 project to the use of formalmodels of coordination and organisation mechanisms to deliver aflexible, high-level means to describe the structure of interactionsbetween services in the environment. We propose to build on thecurrent activities in service-oriented engineering by defining threelevels: (i) An organisational level models the organisational structure of executing and interlinked services and the context aroundthem. (ii) A coordination level provides flexible ways to model interaction between the services. (iii) These two levels connect withexisting (semantic) Web services, which contain semantic descriptions to make components aware of their social context and of therules of engagement with other services.

AAMAS Conference 2008 Conference Paper

Engineering Large-scale Distributed Auctions

• Peter Gradwell
• Michel Oey
• Reinier Timmer
• Julian Padget
• Frances Brazier

The functional characteristics of market-based solutions are typically best observed through the medium of simulation, data-gathering and subsequent visualization. We previously developed a simulation of multiple distributed auctions to handle resource allocation (in fact, bundles of unspecified goods) and in this paper we want to deploy an equivalent system as a distributed application. There are two notable problems with the simulation-first, application-second approach: (i) the simulation cannot reasonably take account of network effects, and (ii) how to recreate in a distributed application the characteristics demonstrated by the mechanism in the simulation. We describe: (i) the refactorings employed in the process of transforming a uni-processor lock-step simulation into a multiprocessor asynchronous system, (ii) some preliminary performance indicators, and (iii) some reflections on our experience which may be useful in building MAS in general.

AAMAS Conference 2008 Conference Paper

Pan-supplier Stock Control in a Virtual Warehouse

• Emad El-Deen El-Akehal
• Julian Padget

We describe the commercial application of agents to the handling of catalogue and stock-control for the selling of books on the internet. The primary characteristic of the target market is (very) low volumes over a (very) large number of items, thus agility and extremely low overheads are the essential factors for a viable business model. Being a new company (established 2004), without legacy software and with the freedom to make new choices, it was decided that the agent abstraction offered both short-term software engineering and longer-term business advantages. This expectation has been borne out in practice, in that it has been possible to construct an e-trading platform, using a 4-person team over a period of a few months, and that is now part of a live business operation handling just over 12, 000 transactions daily. In this paper we explain how agents helped focus attention on the responsibilities of key software functions, how different functions should interact with one another and how to identify and propagate key performance indicator information through the system to detect unexpected behaviour. Agent technology has many potential benefits for dynamic fast-moving businesses where software requirements change quickly and business needs grow rapidly, all within a dynamic environment that has entirely different rules across the axes of geography, market, customer and competitor. Using autonomous agents allowed The Book Depository to build quickly a complex network of P2P relationships with a large number of suppliers and publishers of very different sizes who each utilize a variety of different trading and data interchange standards.

AAMAS Conference 2005 Conference Paper

Agent-based Matchmaking of Mathematical Web Services

• Simone Ludwig
• Omer Rana
• Bill Naylor
• Julian Padget