Autor:
Orejas, Fernando

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E-mails conocidos

orejas@lsi.upc.edu
orejas@cs.upc.edu

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Orejas

Nombre de pila

Fernando

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Afiliaciones conocidas

Universitat Politècnica de Catalunya, Spain
UPC, Spain

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http://www.lsi.upc.es/~orejas/
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2022 - 20243
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Fecha de inicio: 2020 × Fecha de finalización: 2024 ×

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Mostrando 1 - 3 de 3
  • Miniatura
    Artículo
    Problemas de confluencia en transformación de grafos: de los pares críticos a los conflictos iniciales.
    Orejas, Fernando. Actas de las XXII Jornadas sobre Programación y Lenguajes (PROLE 2023), 2023-09-12.
    Mucha gente cree que la transformación de grafos no es nada más que una generalización de la reescritura de términos. Sin embargo, en este tutorial vetemos que la técnica que se usa en reescritura de términos para la comprobación de la confluencia, el cálculo de los pares críticos y la comprobación de su convergencia, genera problemas serios cuando se adapta a la transformación de grafos. Adicionalmente, veremos cómo se resuelven, en mayor o menor medida, estos problemas a traves del nuevo concepto de conflicto inicial.
  • Miniatura
    Artículo
    Towards a Logical Approach to Graph Databases
    Pino, Elvira; Orejas, Fernando; Mylonakis, Nicos; Pasarella, Edelmira. Actas de las XXI Jornadas de Programación y Lenguajes (PROLE 2022), 2022-09-05.
    Graph databases are now playing an important role, not only because they allow us to overcome some limitations of relational databases, but also because they provide a good model for searching the web. In particular, graph databases differ from relational databases in that the topology of data is as important as the data itself. Thus, typical graph database queries are navigational, asking whether some nodes are connected by paths satisfying some specific properties. While relational databases were designed upon logical and algebraic foundations, the development of graph databases has been quite ad-hoc. In this sense, the aim of this paper is to provide them with some logical foundations. More precisely, in previous work we introduced a navigational logic, called +AFw-GNL+AFw (Graph Navigational Logic) that allows us to describe graph navigational properties. Moreover, this logic is equipped with a deductive tableau method that we proved to be sound and complete. In the current paper, we show how graph queries +AHsAXA-it +AOA la+AH0 Cypher can be expressed using a fragment of +AFw-GNL, defining for them a logical and an operational semantics. Moreover, we show that this operational semantics is sound and complete.
  • Miniatura
    Artículo
    The Semantics of GQL-like Path Queries
    Orejas, Fernando; Pino, Elvira. Actas de las XXIII Jornadas de Programación y Lenguajes (PROLE 2024), 2024-06-17.
    The success of graph databases (GDBs) has caused the development of several dozens of GDB products by companies like Neo4j, Oracle, Amazon, IBM or SAP. In parallel, several graph query languages have been designed for querying these GDBs, like Cypherfor Neo4j, PGQL for Oracle, or GSQL for TigerGraph, which actually are quite similar. This situation has led to propose the creation of a unifying standard for graph query languages. This standard is currently under development, and is called GQL. However, GQL has gone beyond the expressive power of the above mentioned languages in several senses. In a previous paper we defined a logical and an operational semantics for a core language similar to Cypher, showing that the operational semantics is sound and complete with respect to the logical one. Now, in the current work, our aim is to redefine the semantics that we gave for Cypher-like languages to a core subset of GQL.