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Publications

2001

Functional Trees for Regression

Authors
Gama, J;

Publication
Advances in Intelligent Data Analysis, 4th International Conference, IDA 2001, Cascais, Portugal, September 13-15, 2001, Proceedings

Abstract
In this paper we present and evaluate a new algorithm for supervised learning regression problems. The algorithm combines a univariate regression tree with a linear regression function by means of constructive induction. When growing the tree, at each internal node, a linear-regression function creates one new attribute. This new attribute is the instantiation of the regression function for each example that fall at this node. This new instance space is propagated down through the tree. Tests based on those new attributes correspond to an oblique decision surface. Our approach can be seen as a hybrid model that combines a linear regression known to have low variance with a regression tree known to have low bias. Our algorithm was compared against to its components, and two simplified versions, and M5 using 16 benchmark datasets. The experimental evaluation shows that our algorithm has clear advantages with respect to the generalization ability when compared against its components and competes well against the state-of-art in regression trees. © Springer-Verlag Berlin Heidelberg 2001.

2001

Model Checking Interactor Specifications

Authors
Campos, JC; Harrison, MD;

Publication
Autom. Softw. Eng.

Abstract
Recent accounts of accidents draw attention to "automation surprises" that arise in safety critical systems. An automation surprise can occur when a system behaves differently from the expectations of the operator. Interface mode changes are one class of such surprises that have significant impact on the safety of a dynamic interactive system. They may take place implicitly as a result of other system action. Formal specifications of interactive systems provide an opportunity to analyse problems that arise in such systems. In this paper we consider the role that an interactor based specification has as a partial model of an interactive system so that mode consequences can be checked early in the design process. We show how interactor specifications can be translated into the SMV model checker input language and how we can use such specifications in conjunction with the model checker to analyse potential for mode confusion in a realistic case. Our final aim is to develop a general purpose methodology for the automated analysis of interactive systems. This verification process can be useful in raising questions that have to be addressed in a broader context of analysis.

2001

Argumentation as distributed belief revision: Conflict resolution in decentralised co-operative multi-agent systems

Authors
Malheiro, B; Oliveira, E;

Publication
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

Abstract
Decentralised co-operative multi-agent systems are computational systems where conflicts are frequent due to the nature of the represented knowledge. Negotiation methodologies, in this case argumentation based negotiation methodologies, were developed and applied to solve unforeseeable and, therefore, unavoidable conflicts. The supporting computational model is a distributed belief revision system where argumentation plays the decisive role of revision. The distributed belief revision system detects, isolates and solves, whenever possible, the identified conflicts. The detection and isolation of the conflicts is automatically performed by the distributed consistency mechanism and the resolution of the conflict, or belief revision, is achieved via argumentation. We propose and describe two argumentation protocols intended to solve different types of identified information conflicts: context dependent and context independent conflicts. While the protocol for context dependent conflicts generates new consensual alternatives, the latter chooses to adopt the soundest, strongest argument presented. The paper shows the suitability of using argumentation as a distributed decentralised belief revision protocol to solve unavoidable conflicts. © Springer-Verlag Berlin Heidelberg 2001.

2001

Wisdom - A UML based architecture for interactive systems

Authors
Nunes, NJ; Cunha, JFE;

Publication
INTERACTIVE SYSTEMS: DESIGN, SPECIFICATION, AND VERIFICATION

Abstract
The UML is recognized to be the dominant diagrammatic modeling language in the software industry. However, it's support for building interactive systems is still acknowledged to be insufficient. In this paper we discuss and identify the major problems using the UML framework for interactive system development, specifically, in what concerns the architectural issues. Here we present a conceptual architectural model that expands the analysis framework of the Unified Process and the UML profile for software development processes. Our proposal leverages on user-interface domain knowledge, fostering coevolutionary development of interactive systems and enabling artifact change between software engineering and human-computer interaction, under the common notation and semantics of the UML.

2001

A CONCEPTUAL FRAMEWORK FOR AGGREGATE MANAGEMENT OF VIRTUAL ENTERPRISES

Authors
Sousa, JP; Azevedo, AL; Soares, AL;

Publication
E-BUSINESS AND VIRTUAL ENTERPRISES: MANAGING BUSINESS-TO-BUSINESS COOPERATION

Abstract
This paper presents a conceptual framework where the development of an information system for aggregate management of virtual / networked enterprises is taking place. Firstly, the general objectives of the system are described. An ontology based development approach is presented, assuming the role of conceptual guidance, both for the requirements analysis and design phases. Finally, a broad specification of aggregate management in this context is described through use cases.

2001

Timing analysis of reliable real-time communication in CAN networks

Authors
Pinho, LM; Vasques, F;

Publication
13TH EUROMICRO CONFERENCE ON REAL-TIME SYSTEMS, PROCEEDINGS

Abstract
The Controller Area Network (CAN) is a fieldbus network with real-time capabilities. It is generally considered that CAN guarantees atomic multicast properties, through its extensive error detection/signalling mechanisms. However, there are error situations where messages can be delivered in duplicate by some receivers or delivered only by a subset of the receivers, leading to inconsistencies in the supported applications. In order to prevent such inconsistencies, a set of atomic multicast protocols is proposed, taking advantage of CAN synchronous properties to minimise its run-time overhead. This paper presents such set of protocols, focusing on the timing analysis of the supported reliable real-time communication. It demonstrates that, in spite of the extra stack of protocols, the real-time capabilities of CAN are preserved, since the predictability of message transfer is guaranteed.

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