Miguel R. Penabad

Bio: Miguel R. Penabad is an academic researcher from University of A Coruña. The author has contributed to research in topics: Tree (data structure) & Ontology (information science). The author has an hindex of 6, co-authored 29 publications receiving 181 citations.

The Galician virtual library

Abstract: Purpose – This study aims to present the digital library Galician virtual library (BVG, for “Biblioteca Virtual Galega”) in GalicianDesign/methodology/approach – The paper shows the objectives pursued by the BVG, its development, putting special emphasis on the main technological challenges, and presents some data about its usageFindings – A digital library can be used to stimulate a lesser‐used language and to promote the culture and tourism of a regionOriginality/value – The paper shows how a digital library can be used to strengthen the Galician language, which is currently categorised as a “Lesser Used Language” in the European Community and to contribute to the preservation and spreading of Galician culture and literary works, either from current authors or from previous documents It also provides a digital publishing house for new authors and opens a communication channel between current authors and their readers Finally, it helps to connect a scattered community like the Galician, offering a c

Efficient Representation of Multidimensional Data over Hierarchical Domains

Abstract: We consider the problem of representing multidimensional data where the domain of each dimension is organized hierarchically, and the queries require summary information at a different node in the hierarchy of each dimension. This is the typical case of OLAP databases. A basic approach is to represent each hierarchy as a one-dimensional line and recast the queries as multidimensional range queries. This approach can be implemented compactly by generalizing to more dimensions the \(k^2\)-treap, a compact representation of two-dimensional points that allows for efficient summarization queries along generic ranges. Instead, we propose a more flexible generalization, which instead of a generic quadtree-like partition of the space, follows the domain hierarchies across each dimension to organize the partitioning. The resulting structure is much more efficient than a generic multidimensional structure, since queries are resolved by aggregating much fewer nodes of the tree.

Using geographical information systems to browse touristic information.

Abstract: The current expansion of Internet makes it one of the most popular places to publish and search for almost any kind of information. In particular, touristic information, not only about tours or information about resources, places, museums or monuments, but also cultural tourism, has gained much attention in the last years. We propose the use of geographical information systems technology (GIS) that provides interfaces capable of displaying interactive maps with information associated to the elements present in such maps. In this paper, we present a Web interface to access touristic information about Galicia (Spain) using GIS technology to easily find any touristic or cultural information. This interface is enclosed in the Galician Virtual Library (http://bvg.udc.es) Web site.

A documental database query language

Abstract: This work presents a natural language based technique to build user interfaces to query document databases through the web. We call such technique Bounded Natural Language (BNL). Interfaces based on BNL are useful to query document databases containing only structured data, containing only text or containing both of them. That is, the underlying formalism of BNL can integrate restrictions over structured and non-structured data (as text).Interfaces using BNL can be programmed ad hoc for any document database but in this paper we present a system with an ontology based architecture in which the user interface is automatically generated by a software module (User Interface Generator) capable of reading and following the ontology. This ontology is a conceptualization of the database model, which uses a label in natural language for any concept in the ontology. Each label represents the usual name for a concept in the real world.The ontology includes general concepts useful when the user is interested in documents in any corpus in the database, and specific concepts useful when the user is interested in a specific corpus. That is, databases can store one or more corpus of documents and queries can be issued either over the whole database or over a specific corpus.The ontology guides the execution of the User Interface Generator and other software modules in such a way that any change in the database does not imply making changes in the program code, because the whole system runs following the ontology. That is, if a modification in the database schema occurs, only the ontology must be changed and the User Interface Generator will produce a new and different user interface adapted to the new database.

Random graphs

Abstract: We will review some of the major results in random graphs and some of the more challenging open problems. We will cover algorithmic and structural questions. We will touch on newer models, including those related to the WWW.

Requirements engineering for web applications: a comparative study

Abstract: The requirements engineering discipline has become more and more important in the last years. Tasks such as the requirements elicitation, the specification of requirements or the requirements validation are essential to assure the quality of the resulting software. The development of Web systems usually involves more heterogeneous stakeholders than the construction of traditional software. In addition, Web systems have additional requirements for the navigational and multimedia aspects as well as for the usability as no training is possible. Therefore a thoroughly requirements analysis is even more relevant. In contrast, most of the methodologies that have been proposed for the development of Web applications focus on the design paying less attention to the requirements engineering. This paper is a comparative study of the requirements handling in Web methodologies showing trends in the use of techniques for capturing, specifying and validating Web requirements.

The containment problem for Real conjunctive queries with inequalities

Abstract: Query containment is a fundamental algorithmic problem in database query processing and optimization. Under set semantics, the query-containment problem for conjunctive queries has long been known to be NP-complete. In real database systems, however, queries are usually evaluated under bag semantics, not set semantics. In particular, SQL queries are evaluated under bag semantics and return multisets as answers, since duplicates are not eliminated unless explicitly requested. The exact complexity of the query-containment problem for conjunctive queries under bag semantics has been an open problem for more than a decade; in fact, it is not even known whether this problem is decidable.Here, we investigate, under bag semantics, the query-containment problem for conjunctive queries with inequalities. It has been previously shown that, under set semantics, this problem is complete for the second level of the polynomial hierarchy. Our main result asserts that, under bag semantics, the query-containment problem for conjunctive queries with inequalities is undecidable. Actually, we establish the stronger result that this problem is undecidable even if the following two restrictions hold at the same time: (1) the queries use just a single binary relation; and (2) the total number of inequalities is bounded by a certain fixed value. Moreover, the same undecidability results hold under bag-set semantics.