Luís Soares Barbosa

Components as coalgebras: the refinement dimension

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.

Component Identification Through Program Slicing

This paper reports on the development of specific slicing techniques for functional programs and their use for the identification of possible coherent components from monolithic code. An associated tool is also introduced. This piece of research is part of a broader project on program understanding and re-engineering of legacy code supported by formal methods.

Specifying software connectors

Orchestrating software components, often from independent suppliers, became a central concern in software construction. Actually, as relevant as components themselves, are the ways in which they can be put together to interact and cooperate in order to achieve some common goal. Such is the role of the so-called software connectors: external coordination devices which ensure the flow of data and enforce synchronization constraints within a component’s network. This paper introduces a new model for software connectors, based on relations extended in time, which aims to provide support for light inter-component dependency and effective external control.

Transposing partial components: an exercise on coalgebraic refinement

A partial component is a process which fails or dies at some stage, thus exhibiting a finite, more ephemeral behaviour man 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.

On Refinement of Generic State-Based Software Components

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.

On semantics and refinement of UML statecharts: a coalgebraic view

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.

Hybrid specification of reactive systems: an institutional approach

This paper introduces a rigorous methodology for requirements specification of systems that react to external stimulus by evolving through different operational modes. In each mode different functionalities are provided. Starting from a classical state-machine specification, the envisaged methodology interprets each state as a different mode of operation endowed with an algebraic specification of the corresponding functionality. Specifications are given in an expressive variant of hybrid logic which is, at a later stage, translated into first-order logic to bring into scene suitable tool support. The papers main contribution is to provide rigorous foundations for the method, framing specification logics as institutions and the translation process as a comorphism between them.

A Relational Model for Confined Separation Logic

Confined separation logic is a new extension to separation logic designed to deal with problems involving dangling references within shared mutable structures. In particular, it allows for reasoning about confinement in object-oriented programs. In this paper, we discuss the semantics of such an extension by defining a relational model for the overall logic, parametric on the shapes of both the store and the heap. This model provides a simple and elegant interpretation of the new confinement connectives and helps in seeking for duals. A number of properties of this logic are proved calculationally.

Process Calculi à la Bird-Meertens

Abstract This paper is an attempt to apply the reasoning principles and calculational style underlying the so-called Bird-Meertens formalism to the design of process calculi, parametrized by a behaviour model. In particular, basically equational and pointfree proofs of process properties are given, relying on the universal characterisation of anamorphisms and therefore avoiding the explicit construction of bisimulations. The developed calculi can be directly implemented on a functional language supporting coinductive types, which provides a convenient way to prototype processes and assess alternative design decisions.

Hybridisation at Work

This paper presents the encoding of the hybridisation method proposed in [MMDB11, DM13] into the Hets platform.