Exploring scenario exploration

Model finders are very popular for exploring scenarios, helping users validate specifications by navigating through conforming model instances. To be practical, the semantics of such scenario exploration operations should be formally defined and, ideally, controlled by the users, so that they are able to quickly reach interesting scenarios. This paper explores the landscape of scenario exploration operations, by formalizing them with a relational model finder. Several scenario exploration operations provided by existing tools are formalized, and new ones are proposed, namely to allow the user to easily explore very similar (or different) scenarios, by attaching preferences to model elements. As a proof-of-concept, such operations were implemented in the popular Alloy Analyzer, further increasing its usefulness for (user-guided) scenario exploration.North Portugal Regional Operational Programme (ON.2 – O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF), within project NORTE-07-0124-FEDER-000062

Simulation under arbitrary temporal logic constraints

Most model checkers provide a useful simulation mode, that allows users to explore the set of possible behaviours by interactively picking at each state which event to execute next. Traditionally this simulation mode cannot take into consideration additional temporal logic constraints, such as arbitrary fairness restrictions, substantially reducing its usability for debugging the modelled system behaviour. Similarly, when a specification is false, even if all its counter-examples combined also form a set of behaviours, most model checkers only present one of them to the user, providing little or no mechanism to explore alternatives. In this paper, we present a simple on-the-fly verification technique to allow the user to explore the behaviours that satisfy an arbitrary temporal logic specification, with an interactive process akin to simulation. This technique enables a unified interface for simulating the modelled system and exploring its counter-examples. The technique is formalised in the framework of state/event linear temporal logic and a proof of concept was implemented in an event-based variant of the Electrum framework.This work is financed by the ERDF - European Regional Development Fund - through the Operational Programme for Competitiveness and Internationalisation - COMPETE 2020 - and by National Funds through the Portuguese funding agency, FCT - Fundação para a Ciência e a Tecnologia, within project POCI-01- 0145-FEDER-016826, and the French Research Agency project FORMEDICIS ANR-16-CE25-0007. The third author was also supported by the FCT sabbatical grant with reference SFRH/BSAB/143106/2018

Exploiting partial knowledge for efficient model analysis

The advancement of constraint solvers and model checkers has enabled the effective analysis of high-level formal specification languages. However, these typically handle a specification in an opaque manner, amalgamating all its constraints in a single monolithic verification task, which often proves to be a performance bottleneck. This paper addresses this issue by proposing a solving strategy that exploits user-provided partial knowledge, namely by assigning symbolic bounds to the problem’s variables, to automatically decompose a verification task into smaller ones, which are prone to being independently analyzed in parallel and with tighter search spaces. An effective implementation of the technique is provided as an extension to the Kodkod relational constraint solver. Evaluation shows that, in average, the proposed technique outperforms the regular amalgamated verification procedure.ERDF - European Regional Development Fund(POCI-01-0145-FEDER-016826)This work is financed by the ERDF – European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation - COMPETE 2020 Programme and by National Funds through the Portuguese funding agency, FCT - Fundação para a Ciência e a Tecnologia within project POCI-01-0145-FEDER-016826.info:eu-repo/semantics/publishedVersio

Platinum: Reusing Constraint Solutions in Bounded Analysis of Relational Logic

Alloy is a light weight specification language based on relational logic, with an analysis engine that relies on SAT solvers to automate bounded verifica- tion of specifications. In spite of its strengths, the reliance of the Alloy Analyzer on computationally heavy solvers means that it can take a significant amount of time to verify software properties, even within limited bounds. This challenge is exacerbated by the ever-evolving nature of complex software systems. This paper presents PLATINUM, a technique for efficient analysis of evolving Alloy specifications, that recognizes opportunities for constraint reduction and reuse of previously identified constraint solutions. The insight behind PLATINUM is that formula constraints recur often during the analysis of a single specification and across its revisions, and constraint solutions can be reused over sequences of anal- yses performed on evolving specifications. Our empirical results show that PLAT- INUM substantially reduces (by 66.4% on average) the analysis time required on specifications extracted from real-world software systems

EvoAlloy: An Evolutionary Approach For Analyzing Alloy Specifications

Using mathematical notations and logical reasoning, formal methods precisely define a program’s specifications, from which we can instantiate valid instances of a system. With these techniques, we can perform a variety of analysis tasks to verify system dependability and rigorously prove the correctness of system properties. While there exist well-designed automated verification tools including ones considered lightweight, they still lack a strong adoption in practice. The essence of the problem is that when applied to large real world applications, they are not scalable and applicable due to the expense of thorough verification process. In this thesis, I present a new approach and demonstrate how to relax the completeness guarantee without much loss, since soundness is maintained. I have extended a widely applied lightweight analysis, Alloy, with a genetic algorithm. Our new tool, EvoAlloy, works at the level of finite relations generated by Kodkod and evolves the chromosomes based on the feedback including failed constraints. Through a feasibility study, I prove that my approach can successfully find solutions to a set of specifications beyond the scope where traditional Alloy Analyzer fails. While EvoAlloy solves small size problems with longer time, its scalability provided by genetic extension shows its potential to handle larger specifications. My future vision is that when specifications are small I can maintain both soundness and completeness, but when this fails, EvoAlloy can switch to its genetic algorithm. Adviser: Hamid Bagher

Towards a quantitative alloy

Dissertação de mestrado integrado em Engenharia InformáticaWhen one comes across a new problem that needs to be solved, by abstracting from its associated details in a simple and concise way through the use of formal methods, one is able to better understand the matter at hand. Alloy (Jackson, 2012), a declarative specification language based on relational logic, is an example of an effective modelling tool, allowing high-level specification of potentially very complex systems. However, along with the irrelevant information, measurable data of the system is often lost in the abstraction as well, making it not as adequate for certain situations. The Alloy Analyzer represents the relations under analysis by Boolean matrices. By extending this type of structure to: • numeric matrices, over N0 , one is able to work with multirelations, i.e. relations whose arcs are weighted; each tuple is thus associated with a natural number, which allows reasoning in a similar fashion as in optimization problems and integer programming techniques; • left-Stochastic matrices, one is able to model faulty behaviour and other forms of quantitative information about software systems in a probabilistic way; in particular, this introduces the notion of a probabilistic contract in software design. Such an increase in Alloy’s capabilities strengthens its position in the area of formal methods for software design, in particular towards becoming a quantitative formal method. This dissertation explores the motivation and importance behind quantitative analysis by studying and establishing theoretical foundations through categorial approaches to accomplish such reasoning in Alloy. This starts by reviewing the required tools to support such groundwork and proceeds to the design and implementation of such a quantitative Alloy extension. This project aims to promote the evolution of quantitative formal methods by successfully achieving quantitative abstractions in Alloy, extending its support to these concepts and implementing them in the Alloy Analyzer.Quando se depara com um novo problema que precisa de ser resolvido, ao abstrair dos seus detalhes associados de forma simples e concisa recorrendo a métodos formais, é possível compreender melhor o assunto em questão. Alloy (Jackson, 2012), uma linguagem de especificação declarativa baseada em lógica relacional, é um exemplo de uma ferramenta de modelação eficaz, possibilitando especificações de alto-nível de sistemas potencialmente bastante complexos. Contudo, em conjunto com a informação irrelevante, os dados mensuráveis são muitas vezes também perdidos na abstração, tornando-a não tão adequada para certas situações. O Alloy Analyzer representa as relações sujeitas a análise através de matrizes Booleanas. Ao estender este tipo de estrutura para: • matrizes numéricas, em N0 , é possível lidar com multirelações, i.e., relações cujos arcos são pesados; cada tuplo é consequentemente associado a um número natural, o que proporciona uma linha de raciocínio semelhante à de técnicas de problemas de otimização e de programação inteira; • matrizes estocásticas, permitindo a modelação de comportamento defeituoso e de outros tipos de informação quantitativa de sistemas de software probabilisticamente; em particular, é introduzida a noção de contrato probabilístico em design de software. Tal aumento às capacidades do Alloy, fortalece a sua posição na área de métodos formais para design de software, em particular, a caminho de se tornar um método formal quantitativo. Esta dissertação explora a motivação e a importância subjacente à análise quantitativa, a partir do estudo e consolidação dos fundamentos teóricos através de abordagens categóricas de forma a conseguir suportar esse tipo de raciocínio em Alloy. Inicialmente, as ferramentas imprescindíveis para assegurar tal base são analisadas, passando de seguida ao planeamento e posterior implementação de tal extensão quantitativa do Alloy. Este projecto pretende promover a evolução dos métodos formais quantitativos através da concretização de abstracção quantitativa em Alloy, estendendo a sua base para suportar estes conceitos e assim implementá los no Alloy Analyzer

A generic approach to model generation operations

Model generation operations are important artifacts in MDE applications. These approaches can be used for model verification, model finding, and others. In many scenarios, model transformations can as well be represented by a model generation operation. This often comes with the advantage of being bidi- rectional and supporting increments. However, most part of model generation approaches do not target several operation kinds, but narrower scenarios by mapping the generation problem into solver specific problems. They are efficient, but often don’t have a supporting framework. In this paper, we present an approach and framework that allows to specify and to execute model operations that can be represented in terms of model generation operations. We first introduce a model search layer that can be used with different solvers. We illustrate this layer with a driving example implemented using Alloy/SAT solver. On top of this, we introduce a transformation layer, which specification are translated into the model search layer, independently from any solver. The solution is natively bidirectional, incremental and it is not restricted to one-and-one scenarios. The approach is illustrated by two use cases and with 3 different scenarios, backed by a full, extensible and free implementation

Fundamental Approaches to Software Engineering

This open access book constitutes the proceedings of the 23rd International Conference on Fundamental Approaches to Software Engineering, FASE 2020, which took place in Dublin, Ireland, in April 2020, and was held as Part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2020. The 23 full papers, 1 tool paper and 6 testing competition papers presented in this volume were carefully reviewed and selected from 81 submissions. The papers cover topics such as requirements engineering, software architectures, specification, software quality, validation, verification of functional and non-functional properties, model-driven development and model transformation, software processes, security and software evolution

Políticas de Copyright de Publicações Científicas em Repositórios Institucionais: O Caso do INESC TEC

A progressiva transformação das práticas científicas, impulsionada pelo desenvolvimento das novas Tecnologias de Informação e Comunicação (TIC), têm possibilitado aumentar o acesso à informação, caminhando gradualmente para uma abertura do ciclo de pesquisa. Isto permitirá resolver a longo prazo uma adversidade que se tem colocado aos investigadores, que passa pela existência de barreiras que limitam as condições de acesso, sejam estas geográficas ou financeiras. Apesar da produção científica ser dominada, maioritariamente, por grandes editoras comerciais, estando sujeita às regras por estas impostas, o Movimento do Acesso Aberto cuja primeira declaração pública, a Declaração de Budapeste (BOAI), é de 2002, vem propor alterações significativas que beneficiam os autores e os leitores. Este Movimento vem a ganhar importância em Portugal desde 2003, com a constituição do primeiro repositório institucional a nível nacional. Os repositórios institucionais surgiram como uma ferramenta de divulgação da produção científica de uma instituição, com o intuito de permitir abrir aos resultados da investigação, quer antes da publicação e do próprio processo de arbitragem (preprint), quer depois (postprint), e, consequentemente, aumentar a visibilidade do trabalho desenvolvido por um investigador e a respetiva instituição. O estudo apresentado, que passou por uma análise das políticas de copyright das publicações científicas mais relevantes do INESC TEC, permitiu não só perceber que as editoras adotam cada vez mais políticas que possibilitam o auto-arquivo das publicações em repositórios institucionais, como também que existe todo um trabalho de sensibilização a percorrer, não só para os investigadores, como para a instituição e toda a sociedade. A produção de um conjunto de recomendações, que passam pela implementação de uma política institucional que incentive o auto-arquivo das publicações desenvolvidas no âmbito institucional no repositório, serve como mote para uma maior valorização da produção científica do INESC TEC.The progressive transformation of scientific practices, driven by the development of new Information and Communication Technologies (ICT), which made it possible to increase access to information, gradually moving towards an opening of the research cycle. This opening makes it possible to resolve, in the long term, the adversity that has been placed on researchers, which involves the existence of barriers that limit access conditions, whether geographical or financial. Although large commercial publishers predominantly dominate scientific production and subject it to the rules imposed by them, the Open Access movement whose first public declaration, the Budapest Declaration (BOAI), was in 2002, proposes significant changes that benefit the authors and the readers. This Movement has gained importance in Portugal since 2003, with the constitution of the first institutional repository at the national level. Institutional repositories have emerged as a tool for disseminating the scientific production of an institution to open the results of the research, both before publication and the preprint process and postprint, increase the visibility of work done by an investigator and his or her institution. The present study, which underwent an analysis of the copyright policies of INESC TEC most relevant scientific publications, allowed not only to realize that publishers are increasingly adopting policies that make it possible to self-archive publications in institutional repositories, all the work of raising awareness, not only for researchers but also for the institution and the whole society. The production of a set of recommendations, which go through the implementation of an institutional policy that encourages the self-archiving of the publications developed in the institutional scope in the repository, serves as a motto for a greater appreciation of the scientific production of INESC TEC