Recent Publications

Almeida PS, Moreno CB, Fonte V.  2007.  Improving on version stamps. On the Move to Meaningful Internet Systems 2007: OTM 2007 Workshops. 4806:1025–1031. Abstract

Optimistic distributed systems often rely on version vectors or their variants in order to track updates on replicated objects. Some of these mechanisms rely on some form of global configuration or distributed naming protocol in order to assign unique identifiers to each replica. These approaches are incompatible with replica creation under arbitrary partitions, a typical operation mode in mobile or poorly connected environments. Other mechanisms assign unique identifiers relying on statistical correctness. In previous work we have introduced an update tracking mechanism that overcomes these limitations. This paper presents results from recent experimentation, that brought to surface a particular pattern of operation that results in an unforeseen, unlimited growth in space consumption. We also describe informally a new update tracking mechanism that does not exhibit this pathological growth while providing guaranteed unique identifiers for a dynamic number of replicas under arbitrary partitions and the same functionality of version vectors.

Barbosa LS, Martinho M.  2007.  Modelling is for reasoning. Mathematical Modelling (ICTMA 12): Education, Engineering and Economics. :480-490. Abstract

In a broad sense, computing is an area of knowledge from which a popular and effective technology emerged long before a solid, specific, scientific methodology, let alone formal foundations, had been put forward. This might explain some of the weaknesses in the software industry, on the one hand, as well as an excessively technology-oriented view which dominates computer science training at pre-university and even undergraduate teaching, on the other. Modelling, understood as the ability to choose the right abstractions for a problem domain, is consensually recognised as essential for the development of true engineering skills in this area, as it is in all other engineering disciplines. But, how can the basic problem-solving strategy, one gets used to from school physics: understand the problem, build a mathematical model, reason within the model, calculate a solution, be taken (and taught) as the standard way of dealing with software design problems? This paper addresses this question, illustrating and discussing the interplay between modelling and reasoning.

Ferreira P, Azevedo PJ.  2007.  Deterministic Motif Mining in Protein Databases. Successes and New Directions in Data Mining. Abstract

Protein sequence motifs describe, through means of enhanced regular expression syntax, regions of amino acids that have been conserved across several functionally related proteins. These regions may have an implication at the structural and functional level of the proteins. Sequence motif analysis can bring significant improvements towards a better understanding of the protein sequence-structure-function relation. In this chapter, we review the subject of mining deterministic motifs from protein sequence databases. We start by giving a formal definition of the different types of motifs and the respective specificities. Then, we explore the methods available to evaluate the quality and interest of such patterns. Examples of applications and motif repositories are described. We discuss the algorithmic aspects and different methodologies for motif extraction. A brief description on how sequence motifs can be used to extract structural level information patterns is also provided.

Campos JC, Harrison M.  2006.  Automated deduction and usability reasoning. Encyclopedia of Human-Computer Interaction. :45-54. Abstract

Reasoning about the usability of a given interactive system's design is a difficult task. However it is one task that must be performed if downstream costs with extensive redesign are to be avoided. Traditional usability testing alone cannot avoid these costs since it too often is performed late in development life cycle. In recent years approaches have been put forward that attempt to reason about the usability of a design from early in development. Mainstream approaches are based on some kind of (more or less structured) inspection of a design by usability experts. This type of approach breaks down for systems with large and complex user interfaces, and again extensive testing is required. In an attempt to deal with these issues there have been attempts to apply software engineering reasoning tools to the development of interactive systems. The article reviews this work and puts forward some ideas for the future.

Fernandes A, Pereira JR, Campos JC.  2006.  Accessibility and Visually Impaired Users. Enterprise Information Systems VI. Abstract

Internet accessibility for the visually impaired community is still an open issue. Guidelines have been issued by the W3C consortium to help web designers to improve web site accessibility. However several studies show that a significant percentage of web page creators are still ignoring the proposed guidelines. Several tools are now available, general purpose, or web specific, to help visually impaired readers. But is reading a web page enough? Regular sighted users are able to scan a web page for a particular piece of information at high speeds. Shouldn't visually impaired readers have the same chance? This paper discusses some features already implemented to improve accessibility and presents a user feedback report regarding the AudioBrowser, a talking browser. Based on the user feedback the paper also suggests some avenues for future work in order to make talking browsers and screen readers compatible.

Oliveira JN, Rodrigues C.  2006.  Pointfree Factorization of Operation Refinement. FM - Formal Methods 2006 . 4085:236–251. Abstract

The standard operation refinement ordering is a kind of “meet of op- posites”: 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 mathe- matically 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 ex- ploit factor instantiation across different subclasses of (relational) operation. The prospect of generalizing the factorization to coalgebraic refinement is discussed.

Cortes B, Oliveira JN.  2006.  Relational Sampling for Data Quality Auditing and Decision Support. Enterprise Information Systems V. :82–88. 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.

Barbosa LS, Sun M, Aichernig B, Rodrigues N.  2006.  On the Semantics of Componentware: a Coalgebraic Perspective. Mathematical Frameworks for Component Software: Models for Analysis and Synthesis. :69–117. Abstract

In this chapter we present a coalgebraic semantics for components. Our semantics forms the basis for a family of operators for combining components. These operators together with their algebraic laws establish a calculus for software components. We present two applications of our semantics: a coalgebraic interpretation of UML diagrams and the design of a component repository.

Barbosa LS.  2005.  A Perspective on Component Refinement. Formal Methods for Components and Objects, Third International Symposium, FMCO 2004, Leiden, The Netherlands, November 2 - 5, 2004, Revised Lectures. 3657:23–48. Abstract

This paper provides an overview of an approach to coalgebraic modelling and refinement of state-based software components, summing up some basic results and introducing a discussion on the interplay between behavioural and classical data refinement. The approach builds on coalgebra theory as a suitable tool to capture observational semantics and to base an abstract characterisation of possible behaviour models for components (from partiality to different degrees of non-determinism).

Ferreira JF, Sobral JL.  2005.  ParC#: Parallel Computing with C# in .NET. Parallel Computing Technologies (LNCS 3606). Abstract

This paper describes experiments with the development of a parallel computing platform on top of a compatible C# implementation: the Mono project. This implementation has the advantage of running on both Windows and UNIX platforms and has reached a stable state. This paper presents performance results obtained and compares these results with implementations in Java/RMI. The results show that the Mono network performance, critical for parallel applications, has greatly improved in recent releases, that it is superior to the Java RMI and is close to the performance of the new Java nio package. The Mono virtual machine is not yet so highly tuned as the Sun JVM and Thread scheduling needs to be improved. Overall, this platform is a new alternative to explore in the future for parallel computing.

Oliveira JN, Rodrigues C.  2004.  Transposing Relations: from Maybe Functions to Hash Tables. MPC - 7th International Conference on Mathematics of Program Construction. 3125:334-356. 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.

Noble J, Vitek J, Lea D, Almeida PS.  1999.  Aliasing in object oriented systems. Object-Oriented Technology ECOOP’99 Workshop Reader. :793–793. Abstract

This chapter contains summaries of the presentations given at the Intercontinental Workshop on Aliasing in Object-Oriented Systems (IWAOOS’99) at the European Conference on Object-Oriented Programming (ECOOP’99) which was held in Lisbon, Portugal on June 15, 1999.

Almeida PS.  1997.  Balloon types: Controlling sharing of state in data types. ECOOP'97—Object-Oriented Programming. :32–59. Abstract

Current data abstraction mechanisms are not adequate to control sharing of state in the general case involving objects in linked structures. The pervading possibility of sharing is a source of errors and an obstacle to language implementation techniques.
We present a general extension to programming languages which makes the ability to share state a first class property of a data type, resolving a long-standing flaw in existing data abstraction mechanisms.
Balloon types enforce a strong form of encapsulation: no state reachable (directly or transitively) by a balloon object is referenced by any external object. Syntactic simplicity is achieved by relying on a non-trivial static analysis as the checking mechanism.
Balloon types are applicable in a wide range of areas such as program transformation, memory management and distributed systems. They are the key to obtaining self-contained composite objects, truly opaque data abstractions and value types—important concepts for the development of large scale, provably correct programs.

Cledou G, Barbosa L.  Submitted.  Modeling Families of Public Licensing Services: A Case Study. FME Workshop on Formal Methods in Software Engineering (FormaliSE). formalise2017.pdf
Neves F, Vilaça R, Pereira JO, Oliveira R.  Submitted.  Prepared Scan: Efficient Retrieval of Structured Data from HBase. {Proceedings of the Symposium on Applied Computing, Sac 2017, Marrakech, Morocco, April 3-7, 2017}. {Part F128005}:{462-464}. Abstractp462-neves.pdf