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Publications

Publications by HASLab

2004

Relational sampling for data quality auditing and decision support

Authors
Cortes, B; Oliveira, JN;

Publication
ICEIS 2004 - Proceedings of the Sixth International Conference on Enterprise Information Systems

Abstract
This paper presents a strategy for applying sampling techniques to relational databases, in the context of data quality auditing or decision support processes. Fuzzy cluster sampling is used to survey sets of records for correctness of business rules. Relational algebra estimators are presented as a data quality-auditing tool.

2004

Iransposing relations: From Maybe functions to hash tables

Authors
de Oliveira, JNF; Rodrigues, CJPC;

Publication
MATHEMATICS OF PROGRAM CONSTRUCTION, PROCEEDINGS

Abstract
Functional transposition is a technique for converting relations into functions aimed at developing the relational algebra via the algebra of functions. This paper attempts to develop a basis for generic transposition. Two instances of this construction are considered, one applicable to any relation and the other applicable to simple relations only. Our illustration of the usefulness of the generic transpose takes advantage of the free theorem of a polymorphic function. We show how to derive laws of relational combinators as free theorems of their transposes. Finally, we relate the topic of functional transposition with the hashing technique for efficient data representation.

2004

On semantics and refinement of UML statecharts: A coalgebraic view

Authors
Sun, M; Zhang, NX; Barbosa, LS;

Publication
PROCEEDINGS OF THE SECOND INTERNATIONAL CONFERENCE ON SOFTWARE ENGINEERING AND FORMAL METHODS

Abstract
Statecharts was conceived as a visual formalism for the design of reactive systems. UML statecharts is an object-based variant of classical statecharts, incorporating several concepts different from the classical statecharts. This paper discusses a coalgebraic description of UML statecharts, directly derived from its operational semantics. In particular such an approach induces suitable notions of equivalence and (behavioral) refinement for statecharts. Finally, a few refinement laws are investigated to support verifiable stepwise system development with statecharts.

2004

On refinement of generic state-based software components

Authors
Meng, S; Barbosa, LS;

Publication
ALGEBRAIC METHODOLOGY AND SOFTWARE TECHNOLOGY: PROCEEDINGS

Abstract
This paper characterizes refinement of state-based software components modelled as pointed coalgebras for some Set endofunctors. The proposed characterization is parametric on a specification of the underlying behaviour model introduced as a strong monad. This provides a basis to reason about (and transform) state-based software designs.

2004

A relational model for component interconnection

Authors
Barbosa, MA; Barbosa, LS;

Publication
JOURNAL OF UNIVERSAL COMPUTER SCIENCE

Abstract
The basic motivation of component based development is to replace conventional programming by the composition of reusable off-the-shelf units, externally coordinated through a network of connecting devices, to achieve a common goal. This paper introduces a new relational model for software connectors and discusses some preliminary work on its implementation in Haskell. The proposed model adopts a coordination point of view in order to deal with components' temporal and spatial decoupling and, therefore, to provide support for looser levels of inter-component dependency and effective external control.

2004

Type-based termination of recursive definitions

Authors
Barthe, G; Frade, MJ; Gimenez, E; Pinto, L; Uustalu, T;

Publication
MATHEMATICAL STRUCTURES IN COMPUTER SCIENCE

Abstract
This paper introduces lambda<^>, a simply typed lambda calculus supporting inductive types and recursive function definitions with termination ensured by types. The system is shown to enjoy subject reduction, strong normalisation of typable terms and to be stronger than a related system in which termination is ensured by a syntactic guard condition. The system can, at will, be extended to support coinductive types and corecursive function definitions also.

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