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El autor Fernando Sáenz-Pérez ha publicado 8 artículo(s):

1 - Restricted Predicates for Hypothetical Datalog

Hypothetical Datalog is based on an intuitionistic semantics rather than on a classical logic semantics, and embedded implications are allowed in rule bodies. While the usual implication (i.e., the neck of a Horn clause) stands for inferring facts, an embedded implication plays the role of assuming its premise for deriving its consequence. A former work introduced both a formal framework and a goal-oriented tabled implementation, allowing negation in rule bodies. While in that work positive assumptions for both facts and rules can occur in the premise, negative assumptions are not allowed. In this work, we cover this subject by introducing a new concept: a restricted predicate, which allows negative assumptions by pruning the usual semantics of a predicate. This new setting has been implemented in the deductive system DES.

Autores: Fernando Sáenz-Pérez / 
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2 - HR-SQL: An SQL Database System with Extended Recursion and Hypothetical Reasoning

In a former work we described the system and language R-SQL that overcomes some limitations of recursion of the relational database language SQL. Such limitations are non-linearity, mutual recursion, and some combinations of negation with recursion. In addition, R-SQL improved termination properties of recursive definitions. Next, this language was extended to include a restricted form of hypothetical relations and queries using assumptions, obtaining the language HR-SQL, and a preliminary implementation was developed for it. Here, we develop a new system HR-SQL from scratch and enhance the former system in several areas. First, hypothetical reasoning is fully integrated with recursive definitions. Second, the Python script generated by the system for computing the extension (materialization) of a database is now targeted to several state-of-the-art relational database systems. Third, the system has been interfaced to the integrated development environment ACIDE, allowing both a more friendly user interaction and a graphical view of the dependency graph that shows dependencies between relations. Fourth, being developed in Prolog, we have targeted it to both SICStus Prolog and SWI-Prolog, also providing standalone executables. Finally, the system has been extended with a bundle of commands, highly improving its capabilities with respect to the former system.

Autores: Susana Nieva / Fernando Sáenz-Pérez / Jaime Sánchez-Hernández / 
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3 - Improving the Deductive System DES with Persistence by Using SQL DBMS’s (Original Work)

This work presents how persistent predicates have been included in the in-memory deductive system DES by relying on external SQL database management systems. We introduce how persistence is supported from a user-point of view and the possible applications the system opens up, as the deductive expressive power is projected to relational databases. Also, we describe how it is possible to intermix computations of the deductive engine and the external database, explaining its implementation and some optimizations. Finally, a performance analysis is undertaken, comparing the system with current relational database systems.

Autores: Fernando Sáenz-Pérez / 
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4 - Improving the Performance of FD Constraint Solving in a CFLP System

Constraint Functional Logic Programming (CFLP) integrates lazy narrowing with constraint solving. It provides a high modeling abstraction, but its solving performance can be penalized by lazy narrowing and solver interface surcharges. As for real-world problems most of the solving time is carried out by solver computations, the system performance can be improved by interfacing state-of-theart external solvers with proven performance. In this work we consider the CFLP system T OY (F D), implemented in SICStus Prolog and supporting Finite Domain (F D) constraints by using its underlying Prolog F D solver. We present a scheme describing how to interface an external CP(F D) solver to T OY (F D), and easily adaptable to other Prolog CLP or CFLP systems. We prove the scheme to be generic enough by interfacing Gecode and ILOG solvers, and we analyze the new performance achieved.

Autores: Ignacio Castiñeiras / Fernando Sáenz-Pérez / 
Palabras Clave: Constraint Functional Logic Programming - Finite Domains Constraint Solving - Solver Integration

5 - Tabling with Support for Relational Features in a Deductive Database

Tabling has been acknowledged as a useful technique in the logic programming arena for enhancing both performance and declarative properties of programs. As well, deductive database implementations benefit from this technique for implementing query solving engines. In this paper, we show how unusual operations in deductive systems can be integrated with tabling. Such operations come from relational database systems in the form of null-related (outer) joins, duplicate support and duplicate elimination. The proposal has been implemented as a proof of concept rather than an efficient system in the Datalog Educational System (DES) using Prolog as a development language and its dynamic database.

Autores: Fernando Sáenz-Pérez / 
Palabras Clave: Deductive databases - DES - Duplicates - Outer Joins - Relational databases - Tabling

6 - Formal Relational Languages in a Deductive Setting

The relational data model coincides with the deductive one and, thus, formal relational query languages can be mapped to a deductive setting. These languages include, on the one hand, Tuple Relational Calculus (TRC) and Domain Relational Calculus (DRC). It can be argued that TRC can be
seen as the formal basis of SQL, while DRC does the same for the semantic web language SPARQL and even the graphical relational language Query-by-Example (QBE). On the other hand, Relational Algebra (RA) is also used as a target language for intermediate compilations from SQL to executable query plans. As commonly acknowledged, RA allows a more formal setting for query optimizations than SQL. In this work, we describe the new support of TRC and DRC in the deductive system DES (which included already SQL and RA) with the aim to have an integrated system for learning database query (formal) languages based on logic.

Autores: Fernando Sáenz-Pérez / 
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7 - Integrating WordNet into Bousi~Prolog (Work in Progress)

In this paper we provide techniques to integrate WordNet into a Fuzzy Logic Programming System. Because WordNet relates words but does not give graded information of the relation between them, we have implemented standard similarity measures and new directives that allow us to generate the proximity equations linking two words with an approximation degree. Proximity equations are the key syntactic structures that, in addition to a weak unification algorithm, make possible a flexible query answering process in this kind of programming languages.

Autores: Pascual Julian-Iranzo / Fernando Saenz-Perez / 
Palabras Clave: Fuzzy Logic Programming - Similarity Measures - WordNet

8 - Experiencing Intuitionistic Logic Programming in SQL Puzzles (Work in Progress)

This work presents some SQL puzzles making use of the application of intuitionistic logic programming (ILP) to implement an SQL system. ILP provides a way of declaring SQL Common Table Expressions as used to specify recursive queries and local view definitions. We present the concepts of ILP that will be used to translate SQL queries to Hypothetical Datalog, providing its syntax, an inference system and translation rules. Then, several novel SQL puzzles used during teaching standard SQL in a database subject are proposed, showing that when following the SQL standard the implemented system is more expressive than current DMBS’s.

Autores: Fernando Saenz-Perez / 
Palabras Clave: Hypothetical Datalog - Intuitionistic Logic Programming - SQL