Owen Cliffe

Answer set programming for representing and reasoning about virtual institutions

It is recognised that institutions are potentially powerful means for making agent interactions effective and efficient, but institutions will only really be useful when, as in other safety-critical scenarios, it is possible to prove that particular properties do or do not hold for all possible encounters. In contrast to symbolic model-checking, answer set programming permits the statement of problems and queries in domain-specific terms as executable logic programs, thus eliminating the gap between specification and verification language. Furthermore, results are presented in the same terms. In this paper we describe the use of answer set programs as an institutional modelling technique. We demonstrate that our institutional model can be intuitively be mapped into an answer set program such that the ordered event traces of the former can be obtained as the answer sets of the latter, allowing for an easy way to query properties of models.

Specifying and analysing agent-based social institutions using answer set programming

In this paper we discuss the use of the Answer Set Programming paradigm for representing and analysing specifications of agent-based institutions. We outline the features of institutions we model, and describe how they are translated into ASP programs which can then be used to verify properties of the specifications. We demonstrate the effectiveness of this approach through the institutions of property and exchange.

LAIMA: a multi-agent platform using ordered choice logic programming

Multi-agent systems (MAS) can take many forms depending on the characteristics of the agents populating them. Amongst the more demanding properties with respect to the design and implementation of multi-agent system is how these agents may individually reason and communicate about their knowledge and beliefs, with a view to cooperation and collaboration. In this paper, we present a deductive reasoning multi-agent platform using an extension of answer set programming (ASP). We show that it is capable of dealing with the specification and implementation of the systems architecture, communication and the individual agents reasoning capacities. Agents are represented as Ordered Choice Logic Programs (OCLP) as a way of modelling their knowledge and reasoning capacities, with communication between the agents regulated by uni-directional channels transporting information based on their answer sets. In the implementation of our system we combine the extensibility of the JADE framework with the flexibility of the OCT front-end to the Smodels answer set solver. The power of this approach is demonstrated by a multi-agent system reasoning about equilibria of extensive games with perfect information.

ASPVIZ: Declarative Visualisation and Animation Using Answer Set Programming

Answer set programming provides a powerful platform for model-based reasoning problems. The answer sets are solutions, but for many non-trivial problems post-processing is often necessary for human readability. In this paper we describe a method and a tool for visualising answer sets in which we exploit answer set programming itself to define how visualisations are constructed. An exciting potential application of our method is to assist in the debugging of answer set programs that, as a consequence of their declarative nature, are not amenable to traditional approaches: visual rendering of answer sets offers a way to help programmers spot false and missing solutions.

Template-Based Adaptation of Semantic Web Services with Model-Driven Engineering

Service-oriented enterprise systems, which tend to be heterogeneous, loosely coupled, long-lived, and continuously running, have to cope with frequent changes to their requirements and the environment. In order to address such changes, applications need to be inherently flexible and adaptive, supported by appropriate infrastructures. In this paper, we propose a model-driven approach for the dynamic adaptation of Web services based on ontology-aware service templates. Model-driven engineering raises the level of abstraction from concrete Web service implementations to high-level service models, which leads to more flexible and automated adaptations through template designs and transformations. The ontological semantics enhances the service matching capabilities required by the dynamic adaptation process. Service templates are based on OWL-S descriptions and provide the necessary means to capture and parameterize specific behavior patterns of service models. In this paper, we apply our approach in the context of the EU-funded ALIVE project and illustrate, as an example, how the proposed framework supports the adaptation of the authentication mechanism used by an interactive tourist recommendation system.

Coordination, Organisation and Model-driven Approaches for Dynamic, Flexible, Robust Software and Services Engineering

Enterprise systems are increasingly composed of (and even functioning as) components in a dynamic, digital ecosystem. On the one hand, this new situation requires flexible, spontaneous and opportunistic collaboration activities to be identified and established among (electronic) business parties. On the other, it demands engineering methods that are able to integrate new functionalities and behaviours into running systems composed by active, distributed, interdependent processes. Here we present a multi-level architecture that combines organisational and coordination theories with model driven development, for the implementation, deployment and management of dynamic, flexible and robust service-oriented business applications, combined with a service layer that accommodates semantic service description, fine-grained semantic service discovery and the dynamic adaptation of services to meet changing circumstances.

Modelling Normative Frameworks Using Answer Set Programing

Norms and regulations play an important role in the governance of human society. Social rules such as laws, conventions and contracts prescribe and regulate our behaviour, however it is possible for us to break these rules at our discretion and face the consequences. By providing the means to describe and reason about norms in a computational context, normative frameworks may be applied to software systems allowing for automated reasoning about the consequences of socially acceptable and unacceptable behaviour. In this paper, we outline our mathematical formulation for normative frameworks and describe how its semantics can be represented in ASP, thus enabling the construction of models of normative systems that can be subjected to formal verification and that can act as functional repositories of normative knowledge for the software components that participate in them.

Embedding landmarks and scenes in a computational model of institutions

Over the last decade, institutions have demonstrated that they are a powerful mechanism to make agent interactions more effective, structured, coordinated and efficient. Different authors have tackled the problem of designing and verifying institutions from different angles. In this paper we propose a formalism that is capable of unifying and extending some of these approaches, as well as providing the necessary tools to assist in the design and verification processes. We demonstrate our approach with a non-trivial case-study.

AQL: A Query Language for Action Domains Modelled Using Answer Set Programming

We present a new general purpose query and abduction language for reasoning about action domains that allows the processing of simultaneous actions, definition of conditions and reasoning about fluents and actions. AQL provides a simple declarative syntax for the specification of constraints on the histories (the combination of action traces and state transitions) within the modelled domain. Its semantics, provided by the translation of AQL queries into Ans-Prolog , acquires the benefits of the reasoning power provided by Answer Set Programming (ASP). The answer sets obtained from combining the query and the domain description correspond to those histories of the domain changing over time that satisfy the query. The result is a simple, high-level query and constraint language that builds on ASP. Through the synthesis of features it offers a more flexible, versatile and intuitive approach compared to existing languages. Due to the use of ASP, AQL can also be used to reason about partial histories.