Technical Reports of Viviana Mascardi

From AUML to WS-BPEL

with G. Casella

The Web Services (WS) technology is currently gaining a wider and wider consensus. The features that characterise WSs, namely heterogeneity, distribution, openness, highly dynamic interactions, are some among the key characteristics of another emerging technology, that of intelligent agents and Multi-Agent Systems (MASs). In this paper we discuss the relationships between WSs and intelligent agents and we propose our point of view, namely that agents provide both the coordination framework and the engineering metaphor that can be exploited for realising complex applications based on the WSs infrastructure. Based on our claim, we suggest to use an agentoriented extension of UML 2.0 named AUML to model agent interaction protocols, and a business protocol execution language for WSs named WS-BPEL, to publish the specification of these protocols on the Web. To demonstrate the feasibility of our approach, we have designed and implemented a tool that automatically creates WS-BPEL and WSDL specifications of interaction protocols starting from AUML visual diagrams.

The PDF version of this paper is available in http://www.disi.unige.it/person/MascardiV/Download/DISI-TR-06-01.pdf

DCaseLP: a Prototyping Environment for Multilingual Agent Systems

with I. Gungui and M. Martelli

This paper describes DCaseLP, a multilingual environment for modelling and prototyping Multi-Agent Systems (MASs). DCaseLP provides an Agent-Oriented Software Engineering (AOSE) methodology which guides the MAS developer from the late requirement analysis stage to the prototype validation stage and offers a set of languages and tools both for modelling agents, and for developing a prototype of the MAS in a semi-automatic way. Full support for validating the MAS model by running the prototype in a JADE platform is offered. DCaseLP has been used to develop an e-commerce application, thus demonstrating the advantages of rapid prototyping in AOSE.

The PDF version of this paper is available in http://www.disi.unige.it/person/MascardiV/Download/tech-rep-05-20.pdf

CaseLP: a Prototyping Environment for Heterogeneous Multi-Agent Systems

with M. Martelli and F. Zini

This paper describes CaseLP, a logic-based environment for modelling and prototyping Multi-Agent Systems (MASs). CaseLP provides an Agent-Oriented Software Engineering (AOSE) methodology which guides the MAS developer from the late requirement analysis stage to the prototype validation stage. CaseLP also offers a set of languages and tools both for modelling agents that are characterised by heterogeneous architectures, and for developing a prototype of the MAS in a semi-automatic way. Full support for validating the MAS model by running the prototype is offered, while limited aid for the formal verification of the MAS properties is supplied. CaseLP has been used to develop real applications in collaboration with industrial partners, thus demonstrating the advantages of rapid prototyping in AOSE.

The compressed postscript version of this paper is available in http://www.disi.unige.it/person/MascardiV/Download/caselp-paper-submitted.ps.gz

Logic-Based Specification Environments for Multi-Agent Systems

Real-world applications are usually characterized by heterogeneous distributed entities that interact following complex coordination protocols and that dynamically and autonomously modify their strategies during this interaction; these systems are extremely difficult to model and implement, and traditional software engineering tools and techniques are often insufficient to cope with this complexity. For this reason a new software engineering paradigm, the Agent-Oriented Software Engineering (AOSE) has joined, over the past ten years, more traditional approaches. AOSE analyzes and designs systems based on the key abstraction of the agent, an autonomous entity situated in some environment, able to perceive the environment itself and to react to changes occurring in it, able to take the initiative when appropriate and capable of communication with other agents in the system. Different approaches have been studied to engineer multi-agent systems (MAS), comprising structured but non-mathematical methodologies as well as logic-based ones. ARPEGGIO, an ongoing software engineering international project involving logic programming groups from USA, Australia and Italy, is designing a logic-based prototyping environment for engineering this kind of complex applications using mainly (but not only) logic-based languages. The focus of this thesis is thus on multi-agent system development environments which use logic-based approaches to specification and implementation. Our contribution is three-fold:
1. We have described many informal and formal approaches to AOSE, with particular attention to the last ones. We have analyzed different kinds of logics and, for each of them, we have provided the description and an example of use of one agent specification languages based on it.
2. We have analyzed some existing MAS Development Kits (MASDKs) to understand which engineering approach, if any, is more commonly adopted and which could be the desiderata for a more powerful environment as ARPEGGIO aims to become. We have compared and drawn a taxonomy of five MASDKs and we have provided rules of thumb to chose the right MASDK to do the right thing.
3. Finally, we have designed the extension of two logic-based MASDKs, IMPACT and CaseLP, with new capabilities. IMPACT has been extended to deal with errors (IMPACT error-tolerant agents), and CaseLP has been extended to become a multi-language distributed environment which could integrate, in the future, the IMPACT specification language, thus taking a first concrete step towards ARPEGGIO's development.

The compressed postscript version of this report is available through anonymous ftp at ftp.disi.unige.it, in /pub/person/MascardiV/Tesi/mythesis.ps.gz (1180320 Bytes).
The uncompressed pdf version of this report is available through anonymous ftp at ftp.disi.unige.it, in /pub/person/MascardiV/Tesi/mythesis.pdf (1712836 Bytes).

Extraction of Significant Terrain Features from RSG and TIN: A Survey

The wide availability of topographic data in digital form has increased interest in terrain modelling and has caused a rapid evolution of Geographic Information Systems (GIS). Research in this field ranges from the early phase of data acquisition to the more complex task of the analytical extraction of landforms from a Digital Terrain Model (DTM). One of the most important issues when working with terrain models is how to extract information on the most significative features of the modelled terrain. The aim of this survey is to offer an outline of algorithms which have been developed for characterizing and extracting surface-specific features from terrain models. Since the algorithm vary according to the model, the survey has been organized as follows: Section 2 introduces the two terrain models we have taken under consideration, namely regular square grids (RSGs) and triangulated irregular networks (TINs) and briefly sketches the contour line model. Section 3 presents some of the most important algorithms for extracting information from an RSG, and Section 4 describes some approaches for extracting features from a TIN. Section 5 concludes the survey with some final considerations.

The compressed postscript version of this paper is available in http://www.disi.unige.it/person/MascardiV/Download/graphics98.ps.gz

The Reduction of the Number of Nullmessages in Conservative LP-Simulation Engines

This document deals with techniques used to reduce the number of nullmessages in a distributed discrete--event simulation. Nullmessages are used to avoid deadlocks which can occurr when simulating physical systems (networks) consisting of one or more physical processes. In the brute--force simplest algorithm [10] the number of nullmessages is very high. Reducing the nullmessages number assures improvements to the simulation performance, and many different solutions have been proposed for this purpose. The document is composed by a survey where these different solutions are presented followed by a comparison between them. A first section introducing the distributed discrete--event simulation general issues makes the document as more self-contained as possible.

The compressed postscript version of this paper is available in http://www.disi.unige.it/person/MascardiV/Download/simulation98.ps.gz