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- Hyperparameter Optimization of a Convolutional Neural Network Model for Pipe Burst Location in Water Distribution NetworksPublication . Antunes, André; Ferreira, Bruno; Marques, Nuno; Carriço, Nélson; DI - Departamento de Informática; NOVALincs; MDPI - Multidisciplinary Digital Publishing InstituteThe current paper presents a hyper parameterization optimization process for a convolutional neural network (CNN) applied to pipe burst locations in water distribution networks (WDN). The hyper parameterization process of the CNN includes the early stopping termination criteria, dataset size, dataset normalization, training set batch size, optimizer learning rate regularization, and model structure. The study was applied using a case study of a real WDN. Obtained results indicate that the ideal model parameters consist of a CNN with a convolutional 1D layer (using 32 filters, a kernel size of 3 and strides equal to 1) for a maximum of 5000 epochs using a total of 250 datasets (using data normalization between 0 and 1 and tolerance equal to max noise) and a batch size of 500 samples per epoch step, optimized with Adam using learning rate regularization. This model was evaluated for distinct measurement noise levels and pipe burst locations. Results indicate that the parameterized model can provide a pipe burst search area with more or less dispersion depending on both the proximity of pressure sensors to the burst or the noise measurement level.
- An algebra of behavioural typesPublication . Ravara, António; Resende, Pedro; T. Vasconcelos, Vasco; DI - Departamento de Informática; CITI - Centro de Informática e Tecnologias da Informação; Academic Press Inc | Elsevier ScienceWe propose a process algebra, the Algebra of Behavioural Types, as a language for typing concurrent objects. A type is a higher-order labelled transition system that characterises all possible life cycles of a concurrent object. States represent interfaces of objects; state transitions model the dynamic change of object interfaces. Moreover, a type provides an internal view of the objects that inhabits it: a synchronous one, since transitions correspond to message reception. To capture this internal view of objects we define a notion of bisimulation, strong on labels and weak on silent actions. We study several algebraic laws that characterise this equivalence, and obtain completeness results for image-finite types.
- Parallel strategies for Direct MultisearchPublication . Tavares, S.; Brás, C. P.; Custódio, A. L.; Duarte, V.; Medeiros, P.; DI - Departamento de Informática; CMA - Centro de Matemática e Aplicações; DM - Departamento de Matemática; NOVALincs; Springer NetherlandsDirect multisearch (DMS) is a derivative-free optimization class of algorithms, suited for computing approximations to the complete Pareto front of a given multiobjective optimization problem. In DMS class, constraints are addressed with an extreme barrier approach, only evaluating feasible points. It has a well-supported convergence analysis and simple implementations present a good numerical performance, both in academic test sets and in real applications. Recently, this numerical performance was improved with the definition of a search step based on the minimization of quadratic polynomial models, corresponding to the algorithm BoostDMS. In this work, we propose and numerically evaluate strategies to improve the performance of BoostDMS, mainly through parallelization applied to the search and to the poll steps. The final parallelized version not only considerably decreases the computational time required for solving a multiobjective optimization problem, but also increases the quality of the computed approximation to the Pareto front. Extensive numerical results will be reported in an academic test set and in a chemical engineering application.
- PS-CRDTsPublication . Barreto, António; Paulino, Hervé; Silva, João A.; Preguiça, Nuno; DI - Departamento de Informática; NOVALincs; North-Holland | ElsevierThe implementation of collaborative applications in highly volatile environments, such as the ones composed of mobile devices, requires low coordination mechanisms. The replication without coordination semantics of Conflict-Free Replicated Data Types (CRDTs) makes them a natural solution for these execution contexts. However, the current CRDT models require each replica to know all other replicas beforehand or to discover them on-the-fly. Such solutions are not compatible with the dynamic ingress and egress of nodes in volatile environments. To cope with this limitation, we propose the Publish/Subscribe Conflict-Free Replicated Data Type (PS-CRDT) model that combines CRDTs with the publish/subscribe interaction model, and, with that, enable the spatial and temporal decoupling of update propagation. We implemented PS-CRDTs in Thyme, a reactive storage system for mobile edge computing. Our experimental results show that PS-CRDTs require less communication than other CRDT-based solutions in volatile environments.
- Surveying communities of users of MATLAB and clone languagesPublication . Reis, Eduardo; Gralha, Catarina; Monteiro, Miguel P.; NOVALincs; ElsevierContext: MATLAB is a programming language vastly used in scientific and engineering domains by engineers, scientists, and researchers. Still, MATLAB seems to be perceived as being used mainly by non-professional programmers, not taking full advantage of MATLAB's features (e.g., OOP-support). The current state of the art does not seem to verify these assumptions. Objectives: Our goal was to fill the gap in the characteristics of the MATLAB community and its users, how proficient they are with the MATLAB, and what is their satisfaction level. Methods: We performed a survey with 212 valid responses, aiming to characterize the community of MATLAB users and clone languages. The survey was published on several platforms, including Reddit, Linkedin, and MATLAB Central. Results: There is a balanced distribution across different levels of experience in the community. (12.74%) of our sample uses MATLAB only through the command window. The more users expect other people to use their programs, the more effort they will put into making the code easy to understand, maintain and reuse. The use of OOP is not widespread (22%). The majority of MATLAB users are satisfied with its modularity support. Conclusions: Our study provides insights into MATLAB's use patterns that are potentially useful for entities responsible for MATLAB's future evolution.
- A social and technical sustainability requirements cataloguePublication . Moreira, Ana; Araújo, João; Gralha, Catarina; Goulão, Miguel; Brito, Isabel Sofia; Albuquerque, Diogo; NOVALincs; CTS - Centro de Tecnologia e Sistemas; ElsevierClimate change calls for action from all sectors of our global economy, including ICT. Therefore, it is important to change the way we develop software to address the challenges posed by sustainability. Our goal is to contribute with a reusable sustainability requirements catalogue that helps developers be aware of sustainability-related properties worth considering during software development. The information for this catalogue was gathered via a systematic mapping study, whose results were synthesised in feature models and then modelled using iStar for a more expressive and configurable representation. A qualitative evaluation of the catalogue's readability, interest, utility, and usefulness by 50 participants from the domain, showed that around 79% of the respondents found the catalogue “Good” or “Very Good”. However, more than 5% of the expert participants found weaknesses regarding most of the evaluated questions and around 25% are neutral in their overall evaluation. This led us to evolve the initial version of the catalogue for the social and technical dimensions of sustainability to improve its completeness and usefulness. This is achieved by aligning the information gathered in the systematic mapping study with the well-established quality model of the ISO/IEC 25010:2011, as we expect most of the experts are familiar with those qualities and respective hierarchies. During this process, we found information that led us to propose two additional qualities that were not covered by the ISO standard: fairness and legislation. We applied this evolved version of the catalogue to the U-Bike project comparing the requirements elicited without the catalogue with those identified using the catalogue. The result suggests that new sustainability requirements were worth considering from a sustainability point of view, supporting the usefulness of the catalogue.
- A Brief History of Updates of Answer-Set ProgramsPublication . Leite, João; Slota, Martin; NOVALincs; DI - Departamento de Informática; Cambridge University PressOver the last couple of decades, there has been a considerable effort devoted to the problem of updating logic programs under the stable model semantics (a.k.a. answer-set programs) or, in other words, the problem of characterising the result of bringing up-to-date a logic program when the world it describes changes. Whereas the state-of-the-art approaches are guided by the same basic intuitions and aspirations as belief updates in the context of classical logic, they build upon fundamentally different principles and methods, which have prevented a unifying framework that could embrace both belief and rule updates. In this paper, we will overview some of the main approaches and results related to answer-set programming updates, while pointing out some of the main challenges that research in this topic has faced.
- A Java typestate checker supporting inheritancePublication . Bacchiani, Lorenzo; Bravetti, Mario; Giunti, Marco; Mota, João; Ravara, António; NOVALincs; Elsevier Science B.V., Amsterdam.Detecting programming errors in software is increasingly important, and building tools that help developers with this task is a crucial area of investigation on which the industry depends. Leveraging on the observation that in Object-Oriented Programming (OOP) it is natural to define stateful objects where the safe use of methods depends on their internal state, we present Java Typestate Checker (JATYC), a tool that verifies Java source code with respect to typestates. A typestate defines the object's states, the methods that can be called in each state, and the states resulting from the calls. The tool statically verifies that when a Java program runs: sequences of method calls obey to object's protocols; objects' protocols are completed; null-pointer exceptions are not raised; subclasses' instances respect the protocol of their superclasses. To the best of our knowledge, this is the first OOP tool that simultaneously tackles all these aspects.
- Using Technology in Digital Humanities for Learning and Knowledge DisseminationPublication . Rodrigues, Armanda; Correia, Nuno Manuel Robalo; DI - Departamento de Informática; NOVALincsAbstract: Research on Digital Humanities (DH) has been boosted due to the investment intechnology for developing access and interaction tools for handling Humanities andHeritage data. The availability of these tools lowers the distance between DHscholars and data generators, and students at various levels, not only because itfacilitates access to information but also through the dissemination technologies usedin these tools, designed for the improvement of user experience. Most of thedisciplines associated with the humanities involve geographical and temporal references, often integrated. These references have been scientifically and pedagogically handled for centuries and are established through the use of maps and timelines. These have been implemented and used digitally and their potential has been risen through their innovative integration with narratives, storytelling and storymaps, enabling the telling of historical events in narratives superimposed on maps.These can be enhanced when supported by rich data, such as images, videos,sound, and their possible combinations in virtual and augmented reality. In thispaper, we describe an initial set of tools which are using a subset of thesetechnologies and data types to enable learning and dissemination of Humanities dataand knowledge. We describe how techniques for making data available and tools forenhancing interaction with these data can improve user experience and potentiatelearning and dissemination. Resumo: A investigação em Humanidades Digitais (DH) desenvolveu-se devido ao investimento em tecnologia para a criação de ferramentas de acesso e interação para o manuseamento de dados de Humanidades e Património. A disponibilização dessas ferramentas diminui a distância entre os especialistas em DH e os seus estudantes a diversos níveis, não só porque estas facilitam o acesso à informação, mas também pelas tecnologias de disseminação utilizadas nessas ferramentas, destinadas à melhoria da experiência do utilizador. A maior parte das disciplinas associadas às humanidades envolve referências geográficas e temporais, muitas vezes integradas. Essas referências têm sido cientificamente e pedagogicamente tratadas há séculos e são estabelecidas através do uso de mapas e linhas do tempo. Estes foram também disponibilizados digitalmente e o seu potencial aumentou graças à integração inovadora em narrativas e em mapas de narrativas, permitindo a disseminação de eventos históricos através da sua sobreposição geográfica em mapas digitais. Estas ferramentas podem ser aperfeiçoadas quando suportadas por dados ricos, como imagens, vídeos, sons e suas possíveis combinações em realidade virtual e aumentada. Neste artigo, descrevemos um conjunto inicial de ferramentas que utilizam um subconjunto destas tecnologias e tipos de dados para permitir a aprendizagem e a disseminação de dados e conhecimentos de Humanidades. Descrevemos ainda como as técnicas para disponibilização de dados e as ferramentas para melhorar a interação com esses dados podem enriquecer a experiência do utilizador e potenciar a aprendizagem e a disseminação.
- From Noisy Point Clouds to Complete Ear ShapesPublication . Valdeira, Filipa; Ferreira, Ricardo; Micheletti, Alessandra; Soares, Cláudia; NOVALincs; DI - Departamento de Informática; Institute of Electrical and Electronics Engineers (IEEE)Ears are a particularly difficult region of the human face to model, not only due to the non-rigid deformations existing between shapes but also to the challenges in processing the retrieved data. The first step towards obtaining a good model is to have complete scans in correspondence, but these usually present a higher amount of occlusions, noise and outliers when compared to most face regions, thus requiring a specific procedure. Therefore, we propose a complete pipeline taking as input unordered 3D point clouds with the aforementioned problems, and producing as output a dataset in correspondence, with completion of the missing data. We provide a comparison of several state-of-the-art registration and shape completion methods, concluding on the best choice for each of the steps.