Type-safe two-level data transformation

A two-level data transformation consists of a type-level transformation of a data format coupled with value-level transformations of data instances corresponding to that format. Examples of two-level data transformations include XML schema evolution coupled with document migration, and data mappings used for interoperability and persistence. We provide a formal treatment of two-level data transformations that is type-safe in the sense that the well-formedness of the value-level transformations with respect to the type-level transformation is guarded by a strong type system. We rely on various techniques for generic functional programming to implement the formalization in Haskell. The formalization addresses various two-level transformation scenarios, covering fully automated as well as user-driven transformations, and allowing transformations that are information-preserving or not. In each case, two-level transformations are disciplined by one-step transformation rules and type-level transformations induce value-level transformations. We demonstrate an example hierarchical-relational mapping and subsequent migration of relational data induced by hierarchical format evolution.Fundação para a Ciência e a Tecnologia (FCT

Relations as executable specifications: taming partiality and non-determinism using invariants

Comunicação publicada em "Lecture Notes in Computer Science", vol. 7560 (2012), pag. 146-161The calculus of relations has been widely used in program specification and reasoning. It is very tempting to use such specifications as running prototypes of the desired program, but, even considering finite domains, the inherent partiality and non-determinism of relations makes this impractical and highly inefficient. To tame partiality we prescribe the usage of invariants, represented by coreflexives, to characterize the exact domains and codomains of relational specifications. Such invariants can be used as pre-condition checkers to avoid runtime errors. Moreover, we show how such invariants can be used to narrow the non-deterministic execution of relational specifications, making it viable for a relevant class of problems. In particular, we show how the proposed techniques can be applied to execute specifications of bidirectional transformations, a domain where partiality and non-determinism are paramount.Fundação para a Ciência e a Tecnologi

Type-safe evolution of spreadsheets

Lecture Notes in Computer Science Volume 6603, 2011Spreadsheets are notoriously error-prone. To help avoid the introduction of errors when changing spreadsheets, models that capture the structure and interdependencies of spreadsheets at a conceptual level have been proposed. Thus, spreadsheet evolution can be made safe within the confines of a model. As in any other model/instance setting, evolution may not only require changes at the instance level but also at the model level. When model changes are required, the safety of instance evolution can not be guarded by the model alone. We have designed an appropriate representation of spreadsheet models, including the fundamental notions of formulæand references. For these models and their instances, we have designed coupled transformation rules that cover specific spreadsheet evolution steps, such as the insertion of columns in all occurrences of a repeated block of cells. Each model-level transformation rule is coupled with instance level migration rules from the source to the target model and vice versa. These coupled rules can be composed to create compound transformations at the model level inducing compound transformations at the instance level. This approach guarantees safe evolution of spreadsheets even when models change.Supported by Fundac ao para a Ciencia e a Tecnologia, grant no. SFRH/BD/30231/2006. Supported by Fundac ao para a Ciencia e a Tecnologia, grant no. SFRH/BD/30215/2006. Work supported by the SSaaPP project, FCT contract no. PTDC/EIA-CCO/108613/200

Transforming data by calculation

Thispaperaddressesthefoundationsofdata-modeltransformation.A catalog of data mappings is presented which includes abstraction and representa- tion relations and associated constraints. These are justified in an algebraic style via the pointfree-transform, a technique whereby predicates are lifted to binary relation terms (of the algebra of programming) in a two-level style encompassing both data and operations. This approach to data calculation, which also includes transformation of recursive data models into “flat” database schemes, is offered as alternative to standard database design from abstract models. The calculus is also used to establish a link between the proposed transformational style and bidi- rectional lenses developed in the context of the classical view-update problem.Fundação para a Ciência e a Tecnologia (FCT

A single complete relational rule for coalgebraic refinement

A transition system can be presented either as a binary relation or as a coalgebra for the powerset functor, each representation being obtained from the other by transposition. More generally, a coalgebra for a functor F generalises transition systems in the sense that a shape for transitions is determined by F, typically encoding a signature of methods and observers. This paper explores such a duality to frame in purely relational terms coalgebraic refinement, showing that relational (data) refinement of transition relations, in its two variants, downward and upward (functional) simulations, is equivalent to coalgebraic refinement based on backward and forward morphisms, respectively. Going deeper, it is also shown that downward simulation provides a complete relational rule to prove coalgebraic refinement. With such a single rule the paper defines a pre-ordered calculus for refinement of coalgebras, with bisimilarity as the induced equivalence. The calculus is monotonic with respect to the main relational operators and arbitrary relator F, therefore providing a framework for structural reasoning about refinement

State-based components made generic

Genericity is a topic which is not sufficiently developed in state-based systems modelling, mainly due to a myriad of approaches and behaviour models which lack unification. This paper adopts coalgebra theory to propose a generic notion of a state-based software component, and an associated calculus, by quantifying over behavioural models specified as strong monads. This leads to the pointfree, calculational reasoning style which is typical of the so-called Bird-Meertens school.(undefined

Will ultrathin CIGS solar cells overtake the champion thin-film cells? Updated SCAPS baseline models reveal main differences between ultrathin and standard CIGS

Cu(In,Ga)Se2 (CIGS) solar cells are amongst the best performing thin-film technologies, with the latest performance gains being mainly due to recent years improvements obtained with post-deposition treatments (PDT). Moreover, thinning of the absorber layer down to sub-micrometre values (ultrathin absorbers) is of extreme importance for CIGS to be even more cost-effective and sustainable. However, electrical and optical limitations, such as rear interface recombination and insufficient light absorption, prevent the widespread implementation of ultrathin CIGS devices. The recent electrical CIGS simulation baseline models have failed to keep up with the experimental developments. Here an updated and experimentally based baseline model for electrical simulations in the Solar Cell Capacitor Simulator (SCAPS) software is presented and discussed with the incorporation of the PDT effects and increased optical accuracy with the support from Finite-Difference Time-Domain (FDTD) simulation results. Furthermore, a champion solar cell with an equivalent architecture validates the developed thin-film model. The baseline model is also applied to ultrathin CIGS solar cell devices, validated with the ultrathin champion cell. Ultimately, these ultrathin models pave the way for an ultrathin baseline model. Simulations results reveal that addressing these absorbers' inherent limitations makes it possible to achieve an ultrathin solar cell with at least 21.0% power conversion efficiency, with open-circuit voltage values even higher than the recent thin-film champion cells.This work was supported by the Fundação para a Ciência e Tecno-logia (FCT) grant numbers DFA/BD/7073/2020, DFA/BD/4564/2020, SFRH/BD/146776/2019, IF/00133/2015, UIDB/50025/2020, UIDP/50025/2020, UIDB/04730/2020, and UIDP/04730/2020. The authors want to acknowledge the funding from the project NovaCell (PTDC/ CTM-CTM/28075/2017). The authors also acknowledge the financial support of the project Baterias 2030, with the reference POCI-01-0247-FEDER-046109, co-funded by Operational Programme for Competitiveness and Internationalization (COMPETE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDFinfo:eu-repo/semantics/submittedVersio

Influência da iluminação LED no desempenho fotossintético e na produtividade de Fragaria x ananassa em substrato

I Congresso Luso-Brasileiro de Horticultura. Sessão Horticultura Herbácea (Olericultura)Durante o crescimento e desenvolvimento das plantas, fatores ambientais como a radiação solar e a temperatura podem ser limitantes no período outono-inverno quando a intensidade luminosa e a temperatura são mais baixas, afetando a atividade fotossintética e a produtividade. Um acréscimo de luz, através do uso de lâmpadas LED (light-emitting diodes), pode minimizar os impactos negativos para a fisiologia da planta em condições menos favoráveis de luminosidade, nomeadamente em zonas temperadas (dias curtos). São poucos os estudos efetuados para avaliar a influência do fator luz no comportamento do morangueiro em termos de eficiência fotossíntetica e nos diferentes componentes da produção, nas condições ambientais portuguesas. Neste sentido, foram avaliados alguns parâmetros fisiológicos e a produtividade de oito cultivares de morangueiro (‘Albión’, ‘Camarosa’, ‘Liberty’, ‘Merced’, ‘Rabida’, ‘Reliance’, ‘San Andreas’ e ‘Splendor’) sujeitas a dois tratamentos de luz (com e sem lâmpadas LED) e conduzidas em dois tipos de substrato [fibra de coco (Coco) e mistura de casca de pinheiro compostada, turfa e fibra de coco (M1)]. O ensaio decorreu no complexo de estufas do INIAV, I.P., em Oeiras e a programação da luz foi diária com início em novembro até ao final de fevereiro. O comportamento fisiológico das plantas foi avaliado em duas fases: floração e plena frutificação. Durante a floração, na maioria dos casos, as plantas sujeitas à luz LED apresentaram maiores valores da taxa fotossintética líquida (Pn) e menores valores de transpiração (E) em relação ao controlo. Este efeito variou entre cultivares e substrato. Na fase de plena frutificação (já sem o tratamento de luz), os valores de Pn foram mais baixos, com diferenças entre cultivares e modalidades de substrato. O teor de clorofilas (SPAD) variou apenas em função da cultivar (p <0,05), nas duas fases de avaliação. Um suplemento de luz durante o outono não influenciou a produtividade das cultivares. A produtividade das plantas conduzidas em substrato Coco foi, em média, 23% superior à das plantas em substrato M1. A maior produtividade ocorreu nas cvs. Rabida, Camarosa e San Andreas. Estes resultados sugerem que o desempenho fotossintético e a produtividade da Fragaria ×ananassa estão mais dependentes do genótipo e do substrato do que da luz adicional. Contudo, um suplemento de luz em condições limitantes de radiação pode contribuir para um melhor desempenho fotossintético das plantas de morangueiroinfo:eu-repo/semantics/publishedVersio

Generic point-free lenses

Lenses are one the most popular approaches to define bidirectional transformations between data models. A bidirectional transformation with view-update, denoted a lens, encompasses the definition of a forward transformation projecting concrete models into abstract views, together with a backward transformation instructing how to translate an abstract view to an update over concrete models. In this paper we show that most of the standard point-free combinators can be lifted to lenses with suitable backward semantics, allowing us to use the point-free style to define powerful bidirectional transformations by composition. We also demonstrate how to define generic lenses over arbitrary inductive data types by lifting standard recursion patterns, like folds or unfolds. To exemplify the power of this approach, we “lensify” some standard functions over naturals and lists, which are tricky to define directly “by-hand” using explicit recursion