Ingeniería Informática
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Browsing Ingeniería Informática by Subject "ALGEBRA"
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artículo de publicación periódica.listelement.badge An algebra for OLAP(2017) Kuijpers, Bart; Vaisman, Alejandro Ariel"Online Analytical Processing (OLAP) comprises tools and algorithms that allow querying multidimensional databases. It is based on the multidimensional model, where data can be seen as a cube, where each cell contains one or more measures can be aggregated along dimensions. Despite the extensive corpus of work in the field, a standard language for OLAP is still needed, since there is no well-defined, accepted semantics, for many of the usual OLAP operations. In this paper, we address this problem, and present a set of operations for manipulating a data cube. We clearly define the semantics of these operations, and prove that they can be composed, yielding a language powerful enough to express complex OLAP queries. We express these operations as a sequence of atomic transformations over a fixed multidimensional matrix, whose cells contain a sequence of measures. Each atomic transformation produces a new measure. When a sequence of transformations defines an OLAP operation, a flag is produced indicating which cells must be considered as input for the next operation. In this way, an elegant algebra is defined. Our main contribution, with respect to other similar efforts in the field is that, for the first time, a formal proof of the correctness of the operations is given, thus providing a clear semantics for them. We believe the present work will serve as a basis to build more solid practical tools for data analysis."capítulo de libro.listelement.badge (Heterogeneous) Structured specifications in logics without interpolation(2018) López Pombo, Carlos G.; Frías, Marcelo"The world of software development has become intrinsically heterogeneous. Many formal languages have been made available to help analysts and designers model different aspects of software. Some examples in the logic realm are equational logic and classical rst-order logic, propositional temporal logics such as LTL and CTL (and their rst-order versions), multimodal logics such as the dynamic logic PDL and its rst-order version, etc. One important feature of a specification language is the existence of structuring mechanisms enabling the modular construction of system descriptions. Structured specifications were introduced by Wirsing for rst-order logic, and later presented in the language-independent setting of institutions by Sannella and Tarlecki. Afterwards, Borzyszkowski presented suffcient conditions for a calculus for (homogeneous) structured speci cations to be complete. These conditions include some form of Craig's interpolation, which results in a scenario that excludes many formalisms employed in the description of software. The contributions of this article are then summarised as follows: a) We present a calculus for structured specifications whose completeness proof does not require any form of interpolation. b)We extend this calculus to a complete calculus for heterogeneous structured specifications."proyecto final de grado.listelement.badge iSurfer: un ray tracer de superficies algebraicas en tiempo real para iPhone(2013) Azar, Daniel José; Modernell, Damián; Prieto, Cristian; Matt, Andreas Daniel"Este es el informe del proyecto final iSurfer de la carrera de Grado de Ingeniería informática en el Instituto Tecnológico de Buenos Aires. El trabajo es el primer graficador de superficies algebraicas en dispositivos móviles utilizando un Raytracer."ponencia en congreso.listelement.badge Querying semantic web data cubes(2016) Etcheverry, Lorena; Vaisman, Alejandro Ariel"We address the problem of querying data cubes for Online Analytical Processing (OLAP) analysis, directly on the Semantic Web (SW). We rst introduce CQL, a simple algebra for querying data cubes at a conceptual level. Taking advantage of QB4OLAP metadata, we automatically translate CQL queries into SPARQL ones, and propose query optimization strategies that adapt, to the particular OLAP set ting, general-purpose techniques. A web application allows exploring and querying OLAP cubes on the SW, using the machinery presented here."ponencia en congreso.listelement.badge An RDF vocabulary for meta-programming with SPARQL algebra(2016) Ceriani, Miguel; Vaisman, Alejandro Ariel"SPARQL queries can be represented in RDF in order to work with them as first-class citizen in Semantic Web applications. The representation used so far, SPIN SPARQL, closely follows the abstract syntax tree, but fails to di rectly capture the semantics and is hard to work with for query rewriting. Here a novel vocabulary based on SPARQL Algebra is presented. The adequacy of the language is empirically shown through a few examples. "