Examinando por Materia "LENGUAJES DE CONSULTA"
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- Ponencia en CongresoAggregation languages for moving object and places of interest(2008) Gómez, Leticia Irene; Kuijpers, Bart; Vaisman, Alejandro Ariel"We address aggregate queries over GIS data and moving object data, where non-spatial information is stored in a data warehouse. We propose a formal data model and query language to express complex aggregate queries. Next, we study the compression of trajectory data, produced by moving objects, using the notions of stops and moves. We show that stops and moves are expressible in our query language and we consider a fragment of this language, consisting of regular expressions to talk about temporally ordered sequences of stops and moves. This fragment can be used not only for querying, but also for expressing data mining and pattern matching tasks over trajectory data."
- Artículo de Publicación PeriódicaAnalytical queries on semantic trajectories using graph databases(2019-10) Gómez, Leticia Irene; Kuijpers, Bart; Vaisman, Alejandro Ariel"This article studies the analysis of moving object data collected by location-aware devices, such as GPS, using graph databases. Such raw trajectories can be transformed into so-called semantic trajectories, which are sequences of stops that occur at “places of interest.” Trajectory data analysis can be enriched if spatial and non-spatial contextual data associated with the moving objects are taken into account, and aggregation of trajectory data can reveal hidden patterns within such data. When trajectory data are stored in relational databases, there is an “impedance mismatch” between the representation and storage models. Graphs in which the nodes and edges are annotated with properties are gaining increasing interest to model a variety of networks. Therefore, this article proposes the use of graph databases (Neo4j in this case) to represent and store trajectory data, which can thus be analyzed at different aggregation levels using graph query languages (Cypher, for Neo4j). Through a real-world public data case study, the article shows that trajectory queries are expressed more naturally on the graph-based representation than over the relational alternative, and perform better in many typical cases."
- Tesis de doctoradoCategorical sequential pattern mining in a spatio-temporal environment(c2009) Gómez, Leticia Irene; Vaisman, Alejandro Ariel"En esta tesis argumentamos que la información de trayectorias también puede ser integrada con datos GIS y OLAP, generando un marco poderoso de análisis".
- Artículo de Publicación PeriódicaEfficient analytical queries on semantic web data cubes(2017-12) Etcheverry, Lorena; Vaisman, Alejandro Ariel"The amount of multidimensional data published on the semantic web (SW) is constantly increasing, due to initiatives such as Open Data and Open Government Data, among other ones. Models, languages, and tools, that allow obtaining valuable information e ciently, are thus required. Multidimensional data are typically represented as data cubes, and exploited using Online Analytical Processing (OLAP) techniques. The RDF Data Cube Vocabulary, also denoted QB, is the current W3C standard to represent statistical data on the SW. Given that QB does not include key features needed for OLAP analysis, in previous work we have proposed an extension, denoted QB4OLAP, to overcome this problem without the need of modifying already published data. Once data cubes are appropriately represented on the SW, we need mechanisms to analyze them. However, in the current state-of-the-art, writing e cient analytical queries over SW data cubes demands a deep knowledge of standards like RDF and SPARQL. These skills are unlikely to be found in typical analytical users. Further, OLAP languages like MDX are far from being easily understood by the final user. The lack of friendly tools to exploit multidimensional data on the SW is a barrier that needs to be broken to promote the publication of such data. This is the problem we address in this paper. Our approach is based on allowing analytical users to write queries using what they know best: OLAP operations over data cubes, without dealing with SW technicalities. For this, we devised CQL (standing for Cube Query Language), a simple, high-level query language that operates over data cubes. Taking advantage of structural metadata provided by QB4OLAP, we translate CQL queries into SPARQL ones. Then, we propose query improvement strategies to produce e cient SPARQL queries, adapting general-purpose SPARQL query optimization techniques. We evaluate our implementation using the Star-Schema benchmark, showing that our proposal outperforms others. The QB4OLAP toolkit,a web application that allows exploring and querying (using CQL) SW data cubes, completes our contributions."
- Artículo de Publicación PeriódicaA model and query language for temporal graph databases(2021-09) Debrouvier, Ariel; Parodi, Eliseo; Perazzo, Matías; Soliani, Valeria; Vaisman, Alejandro Ariel"Graph databases are becoming increasingly popular for modeling different kinds of networks for data analysis. They are built over the property graph data model, where nodes and edges are annotated with property-value pairs. Most existing work in the field is based on graphs were the temporal dimension is not considered. However, time is present in most real world problems. Many different kinds of changes may occur in a graph as the world it represents evolves across time. For instance, edges, nodes, and properties can be added and/or deleted, and property values can be updated. This paper addresses the problem of modeling, storing, and querying temporal property graphs, allowing keeping the history of a graph database. This paper introduces a temporal graph data model, where nodes and relationships contain attributes (properties) timestamped with a validity interval. Graphs in this model can be heterogeneous, that is, relationships may be of different kinds. Associated with the model, a high-level graph query language, denoted T-GQL, is presented, together with a collection of algorithms for computing different kinds of temporal paths in a graph, capturing different temporal path semantics. T-GQL can express queries like “Give me the friends of the friends of Mary, who lived in Brussels at the same time than her, and also give me the periods when this happened”. As a proof-of-concept, a Neo4j-based implementation of the above is also presented, and a client-side interface allows submitting queries in T-GQL to a Neo4j server. Finally, experiments were carried out over synthetic and real-world data sets, with a twofold goal: on the one hand, to show the plausibility of the approach; on the other hand, to analyze the factors that affect performance, like the length of the paths mentioned in the query, and the size of the graph."
- Tesis de doctoradoUn modelo y lenguaje de consulta genérico para el procesamiento analítico online y su aplicación a campos de datos continuos(2014) Gómez, Silvia Alicia; Vaisman, Alejandro Ariel"El análisis de los datos históricos es crucial para la gestión estratégica y la toma de decisiones en diferentes tipos de organizaciones, desde empresas comerciales hasta entidades gubernamentales o civiles. A diferencia de los inicios, la proliferación actual de datos útiles supera los límites de las propias organizaciones. Por otra parte, los datos que se incorporan al análisis organizacional son muy complejos, involucrando imágenes, funcionalidades geográficas, mapas satelitales, web logs, información de redes sociales y datos de bioinformática, entre otros."
- Proyecto final de GradoTemporal graph visualizer(2020-11-17) Orlando, Diego; Ormachea, Joaquín; Vaisman, Alejandro Ariel; Aizemberg, Diego Ariel"Real world scenarios are increasingly being represented with graph databases. Networks in general, and social networks in particular, can be represented as node in a graph, linked through edges. When relationships and node include temporal information, the graphs are called temporal. Temporal graphs are then, graphs that keep track of the history of their nodes and edges. Although these scenarios are normally found in real-world scenarios, there is no tool in the market that can handle appropriately the temporal dimension in graphs. The present work introduces a platform to address this problem. The framework presented here allows displaying temporal graphs and navigating them across time. The result of queries expressed in a high level temporal query language can also be captured and navigated using this tool."
- Ponencia en CongresoTemporal SOLAP: query language, implementation, and a use case(2012) Bisceglia, Pablo; Gómez, Leticia Irene; Vaisman, Alejandro Ariel"The integration of Geographic Information Systems (GIS) and On-Line Analytical Processing (OLAP), denoted SOLAP, is aimed at exploring and analyzing spatial data. In real-world SOLAP applications, spatial and non-spatial data are subject to changes. In this paper we present a temporal query language for SOLAP, called TPiet-QL, supporting so-called discrete changes (for example, in land use or cadastral applications there are situations where parcels are merged or split). TPiet-QL allows expressing integrated GIS-OLAP queries in an scenario where spatial objects change across time. We also present a prototype implementation, and show how this application is used in a real-world scenario: the analysis of protected areas in Uruguay."
- Artículo de Publicación PeriódicaTime-series-based queries on stable transportation networks equipped with sensors(2021) Bollen, Erik; Hendrix, Rik; Kuijpers, Bart; Vaisman, Alejandro Ariel"In this paper, we propose a formalism to query transportation networks that are equipped with sensors that produce time-series data. The core of the proposed query mechanism is a logic based language that is capable to return time, value, and time-series outputs, as well as Boolean queries. We can also use the language for node selection and path selection. Furthermore, we propose an implementation of this language in a graph database system and evaluate its working on a fragment of the Flemish river system that is equipped with sensors that measure the water height at regular moments in time."