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Publications

Publications by Luís Soares Barbosa

2015

Modelling and Verifying Smell-Free Architectures with the ARCHERY Language

Authors
Sanchez, A; Barbosa, LS; Madeira, A;

Publication
SOFTWARE ENGINEERING AND FORMAL METHODS, SEFM 2014

Abstract
Architectural (bad) smells are design decisions found in software architectures that degrade the ability of systems to evolve. This paper presents an approach to verify that a software architecture is smell-free using the Archery architectural description language. The language provides a core for modelling software architectures and an extension for specifying constraints. The approach consists in precisely specifying architectural smells as constraints, and then verifying that software architectures do not satisfy any of them. The constraint language is based on a propositional modal logic with recursion that includes: a converse operator for relations among architectural concepts, graded modalities for describing the cardinality in such relations, and nominals referencing architectural elements. Four architectural smells illustrate the approach.

2015

On the verification of architectural reconfigurations

Authors
Sanchez, A; Madeira, A; Barbosa, LS;

Publication
COMPUTER LANGUAGES SYSTEMS & STRUCTURES

Abstract
In a reconfigurable system, the response to contextual or internal change may trigger reconfiguration events which, on their turn, activate scripts that change the system's architecture at runtime. To be safe, however, such reconfigurations are expected to obey the fundamental principles originally specified by its architect. This paper introduces an approach to ensure that such principles are observed along reconfigurations by verifying them against concrete specifications in a suitable logic. Architectures, reconfiguration scripts, and principles are specified in ARCHERY, an architectural description language with formal semantics. Principles are encoded as constraints, which become formulas of a two-layer graded hybrid logic, where the upper layer restricts reconfigurations, and the lower layer constrains the resulting configurations. Constraints are verified by translating them into logic formulas, which are interpreted over models derived from ARCHERY specifications of architectures and reconfigurations. Suitable notions of bisimulation and refinement, to which the architect may resort to compare configurations, are given, and their relationship with modal validity is discussed.

2016

Proof theory for hybrid(ised) logics

Authors
Neves, R; Madeira, A; Martins, MA; Barbosa, LS;

Publication
SCIENCE OF COMPUTER PROGRAMMING

Abstract
Hybridisation is a systematic process along which the characteristic features of hybrid logic, both at the syntactic and the semantic levels, are developed on top of an arbitrary logic framed as an institution. In a series of papers this process has been detailed and taken as a basis for a specification methodology for reconfigurable systems. The present paper extends this work by showing how a proof calculus (in both a Hilbert and a tableau based format) for the hybridised version of a logic can be systematically generated from a proof calculus for the latter. Such developments provide the basis for a complete proof theory for hybrid(ised) logics, and thus pave the way to the development of (dedicated) proof support.

2015

Specifying Structural Constraints of Architectural Patterns in the ARCHERY Language

Authors
Sanchez, A; Barbosa, LS; Riesco, D;

Publication
PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2014 (ICNAAM-2014)

Abstract
ARCHERY is an architectural description language for modelling and reasoning about distributed, heterogeneous and dynamically reconfigurable systems in terms of architectural patterns. The language supports the specification of architectures and their reconfiguration. This paper introduces a language extension for precisely describing the structural design decisions that pattern instances must respect in their (re)configurations. The extension is a propositional modal logic with recursion and nominals referencing components, i.e., a hybrid mu-calculus. Its expressiveness allows specifying safety and liveness constraints, as well as paths and cycles over structures. Refinements of classic architectural patterns are specified.

2013

Bisimilarity and refinement for hybrid(ised) logics

Authors
Madeira, A; Martins, MA; Barbosa, LS;

Publication
Proceedings 16th International Refinement Workshop, Refine 2013, Turku, Finland, 11th June 2013.

Abstract
The complexity of modern software systems entails the need for reconfiguration mechanisms governing the dynamic evolution of their execution configurations in response to both external stimulus or internal performance measures. Formally, such systems may be represented by transition systems whose nodes correspond to the different configurations they may assume. Therefore, each node is endowed with, for example, an algebra, or a first-order structure, to precisely characterise the semantics of the services provided in the corresponding configuration. Hybrid logics, which add to the modal description of transition structures the ability to refer to specific states, offer a generic framework to approach the specification and design of this sort of systems. Therefore, the quest for suitable notions of equivalence and refinement between models of hybrid logic specifications becomes fundamental to any design discipline adopting this perspective. This paper contributes to this effort from a distinctive point of view: instead of focussing on a specific hybrid logic, the paper introduces notions of bisimilarity and refinement for hybridised logics, i.e. standard specification logics (e.g. propositional, equational, fuzzy, etc) to which modal and hybrid features were added in a systematic way. © A. Madeira, M.A. Martins & L.S. Barbosa.

2013

Giving Alloy a family

Authors
Neves, R; Madeira, A; Martins, MA; Barbosa, LS;

Publication
Proceedings of the 2013 IEEE 14th International Conference on Information Reuse and Integration, IEEE IRI 2013

Abstract
Lightweight formal methods ought to provide to the end user the rigorousness of mathematics, without compromising simplicity and intuitiveness. Alloy is a powerful tool, particularly successful on this mission. Limitations on the verification side, however, are known to prevent its wider use in the development of safety or mission critical applications. A number of researchers proposed ways to connect Alloy to other tools in order to meet such challenges. This paper's proposal, however, is not establishing a link from Alloy to another single tool, but rather to 'plunge' it into the Hets network of logics, logic translators and provers. This makes possible for Alloy specifications to 'borrow' the power of several, non dedicated proof systems. Semantical foundations for this integration are discussed in detail. © 2013 IEEE.

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