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.

Abstract
A partial component is a process which fails or dies at some stage, thus exhibiting a finite, more ephemeral behaviour than expected. Partiality-which is the rule rather than exception in formal modelling-can be treated mathematically via totalization techniques. In the case of partial functions, totalization involves error values and exceptions. In the context of a coalgebraic approach to component semantics, this paper argues that the behavioural counterpart to such functional techniques should extend behaviour with try-again cycles preventing from component collapse, thus extending totalization or transposition from the algebraic to the coalgebraic context. We show that a refinement relationship holds between original and totalized components which is reasoned about in a coalgebraic approach to component refinement expressed in the pointfree binary relation calculus. As part of the pragmatic aims of this research, we also address the factorization of every such totalized coalgebra into two coalgebraic components-the original one and an added front-end-which cooperate in a client-server style.

Abstract
The standard operation refinement ordering is a kind of "meet of opposites": non-determinism reduction suggests "smaller" behaviour while increase of definition suggests "larger" behaviour. Groves' factorization of this ordering into two simpler relations, one per refinement concern, makes it more mathematically tractable but is far from fully exploited in the literature. We present a pointfree theory for this factorization which is more agile and calculational than the standard set-theoretic approach. In particular, we show that factorization leads to a simple proof of structural refinement for arbitrary parametric types and exploit factor instantiation across different subclasses of (relational) operation. The prospect of generalizing the factorization to coalgebraic refinement is discussed.

Abstract
View synchronous group communication is a mature technology that greatly eases the development of reliable distributed applications by enforcing precise message delivery semantics, especially in face of faults. It is therefore found at the core of multiple widely deployed and used middleware products. Although the implementation of a group communication system is a complex task, application developers may benefit from the fact that multiple group communication toolkits are currently available and supported. Unfortunately, each communication toolkit has a different interface, that differs from every other interface in subtle syntactic and semantic aspects. This hinders the design, implementation and maintenance of applications using group communication and forces developers to commit beforehand to a single toolkit, thus imposing a significant hurdle to portability. In this paper we propose jGCS, a generic group communication service for Java, that specifies an interface as well as minimum semantics that allow application portability. This interface accommodates existing group communication services, enabling implementation independence. Furthermore, it provides support for the latest state-of-art mechanisms that have been proposed to improve the performance of group-based applications. To support our claims, we present and experimentally evaluate implementations of jGCS for several major group communication systems, namely, Appia, Spread/FlushSpread and JGroups, and describe the port of a large middleware product to jGCS.

Abstract

Abstract
This paper characterises refinement of state-based software components modelled as pointed coalgebras for some Set endofunctors. The proposed characterisation 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. In particular, it is shown how refinement can be applied to the development of the inequational subset of a calculus of generic software components.