Antonio Becerra-Terón

Querying xml documents in logic programming

Extensible Markup Language (XML) is a simple, very flexible text format derived from SGML. Originally designed to meet the challenges of large-scale electronic publishing, XML is also playing an increasingly important role in the exchange of a wide variety of data on the Web and elsewhere. XPath language is the result of an effort to provide address parts of an XML document. In support of this primary purpose, it becomes in a query language against an XML document. In this paper we present a proposal for the implementation of the XPath language in logic programming. With this aim we will describe the representation of XML documents by means of a logic program. Rules and facts can be used for representing the document schema and the XML document itself. In particular, we will present how to index XML documents in logic programs: rules are supposed to be stored in main memory, however facts are stored in secondary memory by using two kind of indexes: one for each XML tag, and other for each group of terminal items. In addition, we will study how to query by means of the XPath language against a logic program representing an XML document. It evolves the specialization of the logic program with regard to the XPath expression. Finally, we will also explain how to combine the indexing and the top-down evaluation of the logic program.

Integrating XQuery and Logic Programming

In this paper we investigate how to integrate the XQuery language and logic programming. With this aim, we represent XML documents by means of a logic program. This logic program represents the document schema by means of rules and the document itself by means of facts. Now, XQuery expressions can be integrated into logic programming by considering a translation (i.e. encoding) of for-let-where-return expressions by means of logic rules and a goal.

A Framework for Goal-Directed Bottom-Up Evaluation of Functional Logic Programs

In this paper we start the design of a functional-logic deductive database language. Given that most logic deductive languages consider bottom-up evaluation as operational mechanism, here we will focus on the development of an operational semantics based on bottom-up evaluation for functional logic languages. As in the logic paradigm, the bottom-up evaluation will consist in a magic transformation for a given program-query into a magic program-query for which the bottom-up evaluation will simulate the top-down one of the original program.

High performance computing for the heliostat field layout evaluation

In Solar Central Receiver Systems (SCRS), the heliostat field is generally the most important subsystem in terms of initial investment and energy losses. Therefore, heliostat field layout needs to be carefully designed and optimized when deploying this kind of power facilities. This optimization procedure can be focused on multiple and heterogeneous criteria depending on particular factors that lead to define different optimization problems based on specific objective functions. However, objective functions defined for this problem are, in general terms, computationally very expensive. This fact may make an exhaustive optimization process infeasible, specially depending on the available resources, and forces particular simplifications at some steps of the process. Fortunately, some of the objective functions defined can benefit from parallelization, even though this idea is not usually pointed out or discussed, and then, become affordable in better conditions. In this paper, the heliostat field optical efficiency, which is a common objective function in this area, is analyzed to be parallelized by three different approaches.

XQuery Testing from XML Schema Based Random Test Cases

In this paper we present the elements of an XQuery testing tool which makes possible to automatically test XQuery programs. The tool is able to systematically generate XML instances (i.e., test cases) from a given XML schema. The number and type of instances is defined by the human tester. These instances are used to execute the given XQuery program. In addition, the tool makes possible to provide an user defined property to be tested against the output of the XQuery program. The property can be specified with a Boolean XQuery function. The tool is implemented as an oracle able to report whether the XQuery program passes the test, that is, all the test cases satisfy the property, as well as the number of test cases used for testing. In the case of the XQuery program fails the testing, the tool shows counterexamples found in the test cases. The tool has been implemented as an XQuery library which makes possible to be used from any XQuery interpreter.

A Safe Relational Calculus for Functional Logic Deductive Databases

In this paper, we present an extended relational calculus for expressing queries in functional-logic deductive databases. This calculus is based on first-order logic and handles relation predicates, equalities and inequalities over partially defined terms, and approximation equations. For the calculus formulas, we have studied syntactic conditions in order to ensure the domain independence property. Finally, we have studied its equivalence w.r.t. the original query language, which is based on equality and inequality constraints.

Automatic Generation of Ecore Models for Testing ATL Transformations

Model transformation testing is crucial to detect incorrect transformations. Buggy transformations can lead to incorrect target models, either violating target meta-model requirements or more complex target model properties. In this paper we present a tool for testing ATL transformations. This tool is an extension of a previously developed tool for testing XML-based languages. With this aim an Ecore to XML Schema transformation is defined which makes to automatically generate random Ecore models possible. These randomly generated Ecore models are used to test ATL transformations. Properties to be tested are specified by OCL constraints, describing input and output conditions on source and target models, respectively.

A relational algebra for functional logic deductive databases

In this paper, we study the integration of functional logic programming and databases by presenting a data model, and a query and data definition language. The data model is adopted from functional logic programming by allowing complex values. The query and data definition language is based on the use of algebra expressions built from a set of algebra operators over an extended relational algebra. In addition, algebra expressions can be used for defining functions, typical in a functional logic program.

Automatic property‐based testing and path validation of XQuery programs

Property‐based testing has gained popularity in recent years in many areas of software development. The specification of assertions/properties helps to understand the semantics of pieces of code, and in modern programming environments, it can serve to test the program behavior. In this paper an XQuery property‐based testing tool is presented, which enables to automatically test XQuery programs. The tool is able to systematically generate XML instances (i.e., test cases) from a given XML schema, and to filter XML instances with input properties specified by the programmer. Additionally, the tool automatically checks output (respectively, input‐output) properties in each output instance (respectively, each pair of input‐output instances). The tool is able to report whether the XQuery program passes the test, that is, if all the test cases satisfy the (input‐)output property, as well as the number of test cases used for testing. In addition, if the XQuery program fails the test, the tool shows counterexamples found in the test cases. Properties are specified with XQuery Boolean functions, and the testing tool has been implemented in XQuery. Additionally, an XQuery path validation tool is presented. This tool is able to detect wrong paths in XQuery expressions. The path validation tool takes as input an XML schema, and it reports those paths on the XQuery program that do not match the XML schema. The path validation tool is a complement to the testing tool rejecting XQuery programs that do not conform to the XML schema. The path validation tool has been also implemented in XQuery. Finally, a web tool has been developed enabling to test and validate XQuery programs.

Querying open street map with XQuery

In this paper we present a library for querying Open Street Map (OSM) with XQuery. This library is based on the well-known spatial operators defined by Clementini and Egenhofer, providing a repertoire of XQuery functions which encapsulate the search on the XML document representing a layer of OSM, and make the definition of queries on top of OSM layers easy. In essence, the library provides a repertoire of OSM Operators for points and lines which, in combination with Higher Order facilities of XQuery, facilitates the composition of queries and the definition of keyword based search geo-localized queries. OSM data are indexed by an R-tree structure, in which points and lines are enclosed by Minimum Bounding Rectangles (MBRs), in order to get shorter answer time.