Viviane Torres da Silva

From a Conceptual Framework for Agents and Objects to a Multi-Agent System Modeling Language

In this paper we propose a multi-agent system modeling language (MAS-ML) that extends UML (Unified Modeling Language) based on structural and dynamic properties presented in a conceptual framework (metamodel) called Taming Agents and Objects (TAO). Our focus is the adaptation according to TAO concepts of the static Class diagram and the interaction Sequence diagram proposed by UML. These two diagrams have been chosen because they are the most commonly used and because it is possible to use them to illustrate both the structural and dynamic aspects of TAO metamodel. We propose a conservative extension of the UML metamodel, which includes agent-related notions that are part of the TAO conceptual framework while preserving all object-related concepts, which constitute the UML metamodel. The main difference between our approach and the others presented in the literature is the clear definition and representation of the elements that compose MASs and their corresponding behavior. In order to extend UML with TAO non-object concepts, it is not possible to use only the three basic extensions mechanisms provided by UML and new metaclasses and stereotypes have been created and associated with the UML metamodel.

Separation of Concerns in Multi-agent Systems: An Empirical Study

With multi-agent systems (MASs) growing in size and complexity, the separation of their concerns throughout the different development phases is crucial to MAS engineers. Separation of concerns is a well-known principle in software engineering to achieve improved reusability and maintainability of complex software. Hence it is necessary to investigate systematically whether ions from object-oriented (OO) software engineering are able to isolate explicitly MAS concerns. This paper presents an empirical study that evaluates the degree to which abstractions associated with two OO techniques enable modularization of MAS concerns. The selected techniques involve basic OO ions, such as classes and objects, and more sophisticated ones, namely design patterns and aspects. The gathered results shown that the use of aspects allowed the construction of a MAS with a significant improvement in the modularization of different concerns. Also, the use of aspects resulted in: (i) fewer lines of code, (ii) fewer design and implementation components, and (iii) lower coupling between the components. However, the aspect-oriented approach produced lower cohesion in the MAS components. Finally, an important finding of this empirical study is that aspects supported a better alignment with higher-level abstractions from agent-oriented design models.

Taming agents and objects in software engineering

Agent-based software engineering has been proposed in addition to object-oriented software engineering as a means of mastering the complexity associated with the development of large-scale distributed systems. However, there is still a poor understanding of the interplay between the notions of agents and objects from a software engineering perspective. Moreover, the many facets of agent-based software engineering are rarely used in the various phases of the software development lifecycle because of the lack of a comprehensive framework to provide the software designers with a clear understanding of the use of these two key abstractions. In this context, this paper presents TAO, an evolving innovative conceptual framework based on agent and object abstractions, which are the foundations for modeling large-scale software systems. The conceptual framework allows for the characterization of large-scale software systems as organizations of passive components, the objects, and autonomous components, the agents, with each of these elements playing roles to interact with each other and to coordinate their actions in order to fulfill system goals.

From the specification to the implementation of norms: an automatic approach to generate rules from norms to govern the behavior of agents

Open multi-agent systems composed of heterogeneous, autonomous and independently designed agents are usually governed by a set of norms. The established norms regulate the behavior of the agents by pointing out their permissions, prohibitions and obligations. This paper presents a normative language to specify norms and proposes the implementation of such norms by using a rule-based system. The implementation is achieved by automatically transforming the specification of each norm of the system into a set of rules used to govern the behavior of the agents according to the norm. The governance system is able to activate and deactivate norms, to point out the norms violations and fulfillments and to inform about punishments and rewards.

Engineering multi-agent systems with aspects and patterns

Objects and agents are software engineering abstractions that have many common concerns. However, agents are more complex entities since they encompass additional concerns: their state is driven by beliefs, goals, capabilities and plans, and their behavior is composed of a number of agency properties such as autonomy, adaptation, interaction, learning, mobility, and collaboration. A multi-agent system usually incorporates multiple objects and types of agents, with each agent type addressing distinct agency concerns. These agency concerns typically overlap and interact with each other, and so a disciplined scheme for composition is required. In this context, this paper presents and compares an aspect-based proposal with a new pattern-based proposal for building multi-agent software. Both proposals have the following goals: (i) minimize the misalignments between high-level agent models and object-oriented designs, (ii) promote the separation of agency concerns, (in) provide explicit support for disciplined composition of agency concerns in complex software agents, (iv) incorporate flexible facilities to build different types of software agents, and (v) allow the production of multi-agent software systems that are easy to understand, maintain and reuse. We demonstrate the applicability of the two proposals through the Portalware system, a Web-based environment f or the development of e-commerce portals.

Using the UML 2.0 activity diagram to model agent plans and actions

The behavior of an agent is defined through the specification of plans and actions. Agents have a set of plans that are selected to be executed according to their goals (and other mental state information). In this paper, we propose the use of UML 2.0 activity diagrams to model agent plans and actions. We consider a plan to be an activity. Both plans and activities are composed of actions and define the action execution sequence. By using some features available in the UML 2.0 activity diagrams and defining some new ones, we demonstrate how these diagrams can be applied to model agent plans and actions.

Modeling multi-agent systems

Emerging from a paradigm different from objects, the modeling of agents requires its own conceptual frameworks, modeling languages, and methodologies.

MAS-ML: a multiagent system modelling language

Multiagent System Modelling Language (MAS-ML) provides a conservative extension to the Unified Modeling Language (UML) 2.1 metamodel in order to accommodate agent-related abstractions such as roles, organisations, plans and protocols. In this paper we present the MAS-ML metamodel by detailing the new concepts introduced in the UML metamodel. In addition, the paper illustrates the new model elements and summarises the three MAS-ML structural diagrams and the two MAS-ML dynamic diagrams.

Using the MAS-ML to model a multi-agent system

The current object-oriented development practice system analysis is documented through UML artifacts such as Class and Sequence diagrams. Since UML is a widely accepted modeling language, it also would be desirable to offer a UML support for the representation of agent-based system analysis artifacts. Although some central UML constructs are suitably matched for agent-based modeling, several improvements must be made to the UML meta-model to achieve this new goal. This paper presents MAS-ML, a UML extension for agent-based system modeling. The use of MAS-ML for modeling agent-based systems is presented with a simple illustrating application.

ContentNet: a framework for the interoperability of educational content using standard IMS

Abstract The World Wide Web arises as a means to facilitate communication and provide an easier user interface to obtain distributed data. The WWW was organized to allow information contained within it to be read by machines, without them needing to be concerned about interpreting the content. With the increase in the volume of information on the Web, finding, accessing and obtaining information from it became extremely difficult. Seeking a solution to this problem, the IMS project, a consortium of academic, commercial and governmental organizations, has been developing and proposing specifications to facilitate the growth and viability of online activities in the area of education. One of the most important activities of the project is the learning process on the Internet, with the possibility of interoperability between different environments to give support to Web-based education. Based on this project and on the need to re-use the contents already present in the Web-based education servers, this work presents an object-oriented framework that facilitates the description, localization and use of educational content available in servers compatible with the IMS project.