Marco A. Casanova

Inclusion dependencies and their interaction with functional dependencies

Abstract Inclusion dependencies, or INDs (which can say, for example, that every manager is an employee) are studied, including their interaction with functional dependencies, or FDs. A simple complete axiomatization for INDs is presented, and the decision problem for INDs is shown to be PSPACE-complete. (The decision problem for INDs is the problem of determining whether or not Σ logically implies a, given a set Σ of INDs and a single IND a). It is shown that finite implication (implication over databases with a finite number of tuples) is the same as unrestricted implications for INDs, although finite implication and unrestricted implication are distinct for FDs and INDs taken together. It is shown that, although there are simple complete axiomatizations for FDs alone and for INDs alone, there is no complete axiomatization for FDs and INDs taken together, in which every rule is k-mary for some fixed k (and in particular, there is no finite complete axiomatization.) Thus, no k-mary axiomatization can fully describe the interaction between FDs and INDs. This is true whether we consider finite implication or unrestricted implication. In the case of finite implication, this result holds, even if no relation scheme has more than two attributes, and if all of the dependencies are unary (a dependency is unary if the left-hand side and right-hand side each contain only one attribute). In the case of unrestricted implication, the result holds, even if no relation scheme has more than three attributes, each FD is unary, and each IND is binary.

Towards a sound view integration methodology

View integration is investigated with the help of three classes of interrelational dependencies, inclusion dependencies, exclusion dependencies and union functional dependencies. The process of view integration is divided into two steps, combination and optimization. View combination consists in defining new interrelational dependencies that capture similarities between different views. The optimization step tries to reduce redundancy and the size of the schema. Finally, general results about interrelational dependencies are presented that lead to an optimization procedure for a restricted class of schemas.

Concurrency Control Problem for Database Systems

Database systems.- General purpose schedulers.- Logs.- Correctness criteria for general purpose schedulers.- Constructing general purpose schedulers.- Conflict-preserving schedulers.- Database description.- Database manipulation.- Concurrent dynamic logic.- Correctness of transaction systems.- Conclusions and directions for future work.

The nested context model for hyperdocuments

This paper describes the nested context model, a conceptual framework for the definition, presentation and browsing of documents. The model carefully combines hypertext links with the concept of context nodes, used to group together sets of nodes. Context nodes can be nested to any depth and, thus, generalize the classical hierarchical organization of documents. The nested context model also defines an abstract and flexible application program interface that captures the idea that different applications may observe the same node in different ways. Finally, the model offers a rich set of operations to explore the double structure of a hyperdocument - that defined by the links and that induced by the nesting of context nodes.

Updating Relational Views

A view is a logical subset of the data base conceptual schema. Providing a facility for supporting views simplifies the user interface, but creates the problem of translating updates on views into equivalent updates on the data base. The translation of a view update may not be unique, it may not even exist or be ill-defined, and it may create inconsistencies in the data base or have side effects on the view. This paper surveys the two basic approaches proposed to solve the view update problem. The first approach suggests treating views as abstract data types so that the definition of a view includes all permissible view updates, together with their translations. The second approach leads to general view update translators and is based either on an analysis of the conceptual schema dependencies or on the concept of view complement to disambiguate view update translations.

TerraLib: An Open Source GIS Library for Large-Scale Environmental and Socio-Economic Applications

This chapter describes TerraLib, an open source GIS software library. The design goal for TerraLib is to support large-scale applications using socio-economic and environmental data. TerraLib supports coding of geographical applications using spatial databases, and stores data in different database management systems including MySQL and PostgreSQL. Its vector data model is upwards compliant with Open Geospatial Consortium (OGC) standards. It handles spatio-temporal data types (events, moving objects, cell spaces, modifiable objects) and allows spatial, temporal, and attribute queries on the database. TerraLib supports dynamic modeling in generalized cell spaces, has a direct runtime link with the R programming language for statistical analysis, and handles large image data sets. The library is developed in C++, and has programming interfaces in Java and Visual Basic. Using TerraLib, the Brazilian National Institute for Space Research (INPE) developed the TerraView open source GIS, which provides functions for data conversion, display, exploratory spatial data analysis, and spatial and non-spatial queries. Another noteworthy application is TerraAmazon, Brazil’s national database for monitoring deforestation in the Amazon rainforest, which manages more than 2 million complex polygons and 60 gigabytes of remote sensing images.

Nested composite nodes and version control in an open hypermedia system

This paper presents a conceptual model for hypermedia systems that, among other features, supports versioning, permits exploring and managing alternate configurations, maintains document histories, supports cooperative work and provides automatic propagation of version changes. In general, the model was designed to minimize the cognitive overhead imposed on the user by version manipulation. The discussion about version control is phrased in terms of the Nested Context Model, but the major ideas apply to any hypermedia conceptual model that offers nested composite nodes. Briefly, nodes that represent versions of the same object at some level of abstraction are grouped together using the concept of version context, support for cooperative work is based on the idea of public hyperbase and private bases, and the problem of version proliferation is addressed using the concept of current perspective. Finally, the paper also presents a generic layered architecture for hypermedia systems with four major interfaces and shows how it matches the conceptual model.

Publishing Statistical Data on the Web

Statistical data is one of the most important sources of information, relevant for large numbers of stakeholders in the governmental, scientific and business domains alike. In this article, we overview how statistical data can be managed on the Web. With OLAP2 Data Cube and CSV2 Data Cube we present two complementary approaches on how to extract and publish statistical data. We also discuss the linking, repair and the visualization of statistical data. As a comprehensive use case, we report on the extraction and publishing on the Web of statistical data describing 10 years of life in Brazil.

Mapping uninterpreted schemes into entity-relationship diagrams: two applications to conceptual schema design

A method of mapping sets of uninterpreted record or relation schemes into entity-relationship diagrams is described and then applied to two conceptual design problems. First, the method is applied to the design of relational databases. It is shown that the method can be interpreted as a normalization procedure that maps a given relational schema into a new schema that represents an entity-relationship diagram. That is, the original schema has an interpretation in terms of higher-order concepts, which helps in understanding the semantics of the database it describes. The second design problem is related to the conversion of conventional file systems to the database approach. The method is used in this context to obtain a database conceptual schema from the description of the conventional system, which is one of the fundamental steps of the conversion process.

Combining a co-occurrence-based and a semantic measure for entity linking

One key feature of the Semantic Web lies in the ability to link related Web resources. However, while relations within particular datasets are often well-defined, links between disparate datasets and corpora of Web resources are rare. The increasingly widespread use of cross-domain reference datasets, such as Freebase and DBpedia for annotating and enriching datasets as well as documents, opens up opportunities to exploit their inherent semantic relationships to align disparate Web resources. In this paper, we present a combined approach to uncover relationships between disparate entities which exploits (a) graph analysis of reference datasets together with (b) entity co-occurrence on the Web with the help of search engines. In (a), we introduce a novel approach adopted and applied from social network theory to measure the connectivity between given entities in reference datasets. The connectivity measures are used to identify connected Web resources. Finally, we present a thorough evaluation of our approach using a publicly available dataset and introduce a comparison with established measures in the field.