Publications

• Oscar Romero and Alberto Abelló. Automating Multidimensional Design from Ontologies (© ACM). In 10th International Workshop on Data Warehousing and OLAP (DOLAP 2007). Lisbon (Portugal), November 2007. Pages 1-8. ACM Press, 2007. ISBN 1-59593-827-5.
  
  

  This paper presents a new approach to automate the multidimensional design of Data Warehouses. In our approach we propose a semi-automatable method aimed to find the business multidimensional concepts from a domain ontology representing different and potentially heterogeneous data sources of our business domain. In short, our method identifies business multidimensional concepts from heterogeneous data sources having nothing in common but that they are all described by an ontology.

• Alberto Abelló, Toni Urpí, M. Elena Rodríguez, and Marc Estévez. Extensión de Moodle para facilitar la corrección automática de cuestionarios y su aplicación en el ámbito de las bases de datos. In MoodleMoot'07 (Moodle). Cáceres (Spain), October 2007.
  
  

  Moodle 1.5 dispone de un módulo de cuestionarios que facilita la gestión de un conjunto de preguntas para su posterior uso en diferentes cuestionarios que pueden ir definiéndose según las necesidades de cada curso. Básicamente, las preguntas pueden ser de opción múltiple o bien de respuesta corta. En caso de preguntas de respuesta corta, la simple presencia de un espacio en blanco de más o de menos en la respuesta del estudiante (respecto a la solución introducida previamente por el profesor) hace que ésta se considere incorrecta. En el ámbito de la docencia en informática, asignaturas como, por ejemplo, "programación" o "bases de datos", el problema es especialmente sangrante, debido a que los enunciados no acostumbran a tener solución única. Es por esto que nos planteamos la posibilidad de desarrollar un nuevo módulo para Moodle que permitiera más posibilidades en la corrección, que la simple comparación carácter a carácter respecto a la solución aportada por el profesor. Así pues, hemos desarrollado un nuevo tipo de cuestionario cuyas preguntas se encuentran en un repositorio externo al Moodle. Cada una de estas preguntas tiene asociado uno o más Servicios Web que son capaces de discernir si la respuesta del estudiante es correcta o no. En nuestro caso, estábamos interesados en la corrección de consultas sobre una base de datos utilizando SQL, pero mediante el mismo módulo conectando con un Servicio Web diferente, se puede corregir cualquier tipo de pregunta, no necesariamente del ámbito de bases de datos. Básicamente, únicamente requiere que la corrección sea objetivable y, en consecuencia, exista un procedimiento que permita realizarla automáticamente.

• Oscar Romero, and Alberto Abelló. MDBE: Una herramienta Automática para el Modelado Multidimensional. Demonstration in Jornadas de Ingeniería del Software y Bases de Datos (JISBD 2007). Zaragoza(Spain), September 2007. Pages 387-388. Thomson Editores, ISBN 978-84-9732-595-0.
  
  

  Para facilitar el proceso de modelado multidimensional de un DW, en este trabajo presentamos MDBE (Multidimensional Design By Examples): nuestra propuesta de herramienta para validar requisitos multidimensionales proporcionados por el usuario final y expresados como consultas SQL sobre las fuentes de datos operacionales. MDBE descompone la consulta SQL de entrada para extraer el conocimiento multidimensional relevante que contiene y acorde con dicha información, deriva un conjunto de esquemas multidimensionales que satisfacen los requisitos (consultas) del usuario. Es decir, nos propone posibles esquemas multidimensionales de forma automática.

• Oscar Romero and Alberto Abelló. On the Need of a Reference Algebra for OLAP (© Springer-Verlag). In 9th International Conference on Data Warehousing and Knowledge Discovery (DaWaK'07). Regensburg (Germany), September, 2007. Pages 99-110, Lecture Notes in Computer Science volume 4654. Springer, 2007. ISSN 0302-9743, ISBN 3-540-28566-0.
  
  

  Although multidimensionality has been widely accepted as the best solution to conceptual modeling, there is not such agreement about the set of operators to handle multidimensional data. This paper presents a comparative of the existing multidimensional algebras trying to find a common backbone, as well as it discusses about the necessity of a reference multidimensional algebra and the current state of the art.

• Oscar Romero and Alberto Abelló. Generating Multidimensional Schemas from the Semantic Web. Poster session in 19th Conference on Advanced Information Systems Engineering (CAiSE'07). Trodheim (Norwey), June 2007.
  
  

  In this paper, we introduce a semi-automatable method aimed to find the business multidimensional concepts from an ontology representing the organization domain. With these premises, our approach falls into the Semantic Web research area, where ontologies play a key role to provide a common vocabulary describing the meaning of relevant terms and relationships among them.

• Stefano Rizzi, Alberto Abelló, Jens Lechtenbörger, and Juan Trujillo. Research in Data Warehouse Modeling and Design: Dead or Alive? (© ACM). In 9th International Workshop on Data Warehousing and OLAP (DOLAP 2006). Arlington (USA), November 2006. Pages 3-10. ACM Press, 2006. ISBN 1-59593-530-4.
  
  

  Multidimensional modeling requires specialized design techniques. Though a lot has been written about how a data warehouse should be designed, there is no consensus on a design method yet. This paper follows from a wide discussion that took place in Dagstuhl, during the Perspectives Workshop "Data Warehousing at the Crossroads", and is aimed at outlining some open issues in modeling and design of data warehouses. More precisely, issues regarding conceptual models, logical models, methods for design, interoperability, and design for new architectures and applications are considered.

• Alberto Abelló, Roberto García, Rosa Gil, Marta Oliva, and Ferran Perdix. Semantic Data Integration in a Newspaper Content Management System (© Springer-Verlag). In 5th International Conference on Ontologies, DataBases, and Applications of Semantics (ODBASE'06) poster session. Lyon (France), October, 2006. Pages 41-41, Lecture Notes in Computer Science volume 4277. Springer, 2006. ISSN 0302-9743, ISBN 3-540-28566-0. See poster
  
  

  A newspaper content management system has to deal with a very heterogeneous information space as the experience in the Diari Segre newspaper has shown us. The greatest problem is to harmonise the different ways the involved users (journalist, archivists&) structure the newspaper information space, i.e. news, topics, headlines, etc. Our approach is based on ontology and differentiated universes of discourse (UoD). Users interact with the system and, from this interaction, integration rules are derived. These rules are based on Description Logic ontological relations for subsumption and equivalence. They relate the different UoD and produce a shared conceptualisation of the newspaper information domain.

• Oscar Romero and Alberto Abelló. Multidimensional Design by Examples (© Springer-Verlag). In 8th International Conference on Data Warehousing and Knowledge Discovery (DaWaK'06). Krakov (Poland), September, 2006. Pages 85-94, Lecture Notes in Computer Science volume 4081. Springer, 2006. ISSN 0302-9743, ISBN 3-540-28566-0.
  
  

  In this paper we present a method to validate user multidi-mensional requirements expressed in terms of SQL queries. Furthermore, our approach automatically generates and proposes the set of multidimensional schemas satisfying the user requirements, from the organizational operational schemas. If no multidimensional schema is generated for a query, we can state that requirement is not multidimensional.

• Alberto Abelló, José Samos, and Fèlix Saltor. YAM²: A Multidimensional Conceptual Model Extending UML (© Elsevier). In Information Systems 31 (6), September, 2006. Pages 541-567. Elsevier, 2006. ISSN 0306-4379.
  
  

  This paper presents a multidimensional conceptual Object-Oriented model for Data Warehousing and OLAP tools, its structures,integrity constraints and query operations. It has been developed as an extension of UML core metaclasses to facilitate its usage, and try to fill the absence of a standard model. Being a UML extension allows reusing modeling constructs and techniques, and integrating multidimensional modeling in more general modeling processes. Moreover,while existing multidimensional models are restricted to the modeling of isolated stars, this paper investigates the representation of several semantically related star schemas. Summarizability and identification constraints can also be represented in the model, and a closed and complete set of algebraic operations has been defined in terms of functions (so that mathematical properties of functions can be smoothly applied).

• Adriana Marotta, Federico Piedrabuena, and Alberto Abelló. Managing Quality Properties in a ROLAP Environment (© Springer-Verlag). In 18th Conference on Advanced Information Systems Engineering (CAiSE'06). Luxemburg, June 2006. Pages 127-141, Lecture Notes in Computer Science volume 4001. Springer, 2006. ISSN 0302-9743, ISBN 3-540-28566-0.
  
  

  In this work we propose, for an environment where multidimensional queries are made over multiple Data Marts, techniques for providing the user with quality information about the retrieved data. This meta-information behaves as an added value over the obtained information or as an additional element to take into account during the proposition of the queries. The quality properties considered are freshness, availability and accuracy. We provide a set of formulas that allow estimating or calculating the values of these properties, for the result of any multidimensional operation of a predefined basic set.

• Oscar Romero and Alberto Abelló. On the Mismatch Between Multidimensionality and SQL. Technical Report LSI-06-32-R. Dept Llenguatges i Sistemes Informàtics (Universitat Politècnica de Catalunya), June 2006.
  
  

  ROLAP tools are intended to ease information analysis and navigation through the whole Data Warehouse. These tools automat-ically generate a query according to the multidimensional operations performed by the end-user, using the relational database technology to implement multidimensionality and consequently, automatically trans-lating multidimensional operations to SQL. In this paper, we consider this automatic translation process in detail and to do so, we present an exhaustive comparative (both theoretical and practical) between the multidimensional algebra and the relational one. Firstly, we discuss about the necessity of a multidimensional algebra with regard to the relational one and later, we thoroughly study those considerations to be made to guarantee the correctness of a cube-query (an SQL query making mul-tidimensional sense). With this aim, we analyze the multidimensional algebra expressiveness with regard to SQL pointing out the features a query must satisfy to make multidimensional sense and we also focus on those problems that can arise in a cube-query due to SQL intrinsic restrictions. The SQL translation of an isolated operation does not rep-resent a problem, but when mixing up the modifications brought about by a set of operations in a single cube-query, some conflicts derived from SQL could emerge depending on the operations involved. Therefore, if these problems are not detected and treated appropriately, the automatic translation can retrieve unexpected results.

• Alberto Abelló, and Fernando Carpani. Using OWL to integrate relational Schemas. Technical Report LSI-06-10-R. Dept Llenguatges i Sistemes Informàtics (Universitat Politècnica de Catalunya), March 2006.
  
  

  Ontologies offer two contributions to the Semantic Web. On the first hand, they show a vocabulary consensus inside a community. On the other hand, they provide reasoning capabilities. In this paper we present a completely automatic translation from relational schemas to OWL, so that inference mechanisms can be used to integrate different schemas, by dealing with structure heterogeneities. The output of the translation algorithm, which explicits functional dependencies in the relational schema, belongs to OWL Full.

• Oscar Romero, and Alberto Abelló. Improving automatic SQL translation for ROLAP tools. In Proceedings of Jornadas de Ingeniería del Software y Bases de Datos (JISBD 2005). Granada (Spain), September 2005. Pages 123-130. Thomson Editores, ISBN 84-9732-434-X.
  
  

  In the last years, despite a vast amount of work have been devoted to modeling multidimensionality, multidimensional algebra translation to SQL have been overlooked. ROLAP tools automatically generate a cubequery according to the operations performed by the user. The SQL translation does not represent a problem when treating isolated operations but when mixing up together modifications brought about by a set of operations in the same cube-query, some conflicts could emerge depending on the operations involved. Therefore, if these problems are not detected and treated appropriately, the automatic translation can retrieve unexpected results. In this paper, we define and classify conflicts raised when automatically translating a multidimensional algebra to SQL, and analyze how to solve or minimize their impact.

• Alberto Abelló, Xavi de Palol, and Mohand-Saïd Hacid. On the Midpoint of a Set of XML Documents (© Springer-Verlag). In 16th International Conference on Database and Expert Systems Applications (DEXA 05). Copenhagen (Denmark), August 2005. Pages 441-450, Lecture Notes in Computer Science volume 3588. Springer, 2005. ISSN 0302-9743, ISBN 3-540-28566-0.
  
  

  The WWW contains a huge amount of documents. Some of them share the subject, but are generated by different people or even organizations. To guarantee the interchange of such documents, we can use XML, which allows to share documents that do not have the same structure. However, it makes dificult to understand the core of such heterogeneous documents (in general, schema is not available). In this paper, we ofer a characterization and algorithm to obtain the midpoint (in terms of a resemblance function) of a set of semi-structured, heterogeneous documents without optional elements. The trivial case of midpoint would be the common elements to all documents. Nevertheless, in cases with several heterogeneous documents this may result in an empty set. Thus, we consider that those elements present in a given amount of documents belong to the midpoint. A exact schema could always be found generating optional elements. However, the exact schema of the whole set may result in overspecialization (lots of optional elements), which would make it useless.

• Alberto Abelló, Xavi de Palol, and Mohand-Saïd Hacid. Approximating the DTD of a set of XML documents. Technical Report LSI-05-7-R. Dept Llenguatges i Sistemes Informàtics (Universitat Politècnica de Catalunya), March 2005.
  
  

  Extended/preliminary version of the previous paper: "On the Midpoint of a Set of XML Documents".

• Alberto Abelló, and Carme Martín. The Data Warehouse: A Temporal Database. In Proceedings of Jornadas de Ingeniería del Software y Bases de Datos (JISBD 2003). Alacant (Spain), November 2003. Pages 675-684. Campobell S.L., ISBN 84-688-3836-5.
  
  

  The aim of this paper is to bring together two research areas, i.e. "Data Warehouses" and "Temporal Databases", involving representation of time. In order to achieve this goal, data warehouse and temporal database research results have been surveyed. Looking at temporal aspects within a data warehouse, more similarities than differences between temporal databases and data warehouses have been found. The first closeness between these areas consists in the possibility of a data warehouse redefinition in terms of a bitemporal database. Another relation is the use of temporal languages in data warehousing. Moreover, the correspondence between advances in temporal evolution and storage, and data warehouses are presented. Finally, Object-Oriented temporal data models contribute to add the integration and subject-orientation that is required by a data warehouse. Therefore, this paper is focussed on how contributions of the temporal database research could benefit data warehouses.

• Alberto Abelló, José Samos, and Fèlix Saltor. Implementing Operations to Navigate Semantic Star Schemas (© ACM). In 6th International Workshop on Data Warehousing and OLAP (DOLAP 2003). New Orleans (USA), November 2003. Pages 56-62. ACM Press, 2003. ISBN 1-58113-727-3.
  
  

  In the last years, lots of work have been devoted to multidimensional modeling, star shape schemas and OLAP operations. However, \foreign{drill-across} has not captured as much attention as other operations. This operation allows to change the subject of analysis keeping the same analysis space we were using to analyze another subject. It is assumed that this can be done if both subjects share exactly the same analysis dimensions. In this paper, besides the implementation of an algebraic set of operations on a RDBMS, we are going to show when and how we can change the subject of analysis in the presence of semantic relationships, even if the analysis dimensions do not exactly coincide.

• Carme Martín, and Alberto Abelló. A Temporal Study of Data Sources to Load a Corporate Data Warehouse (© Springer-Verlag). In 5th International Conference on Data Warehousing and Knowledge Discovery (DaWaK 2003). Prague (Czech Republic), September 2003. Pages 109-118, Lecture Notes in Computer Science volume 2737. Springer, 2003. ISSN 0302-9743, ISBN 3-540-40807-X.
  
  

  The input data of the corporate data warehouse is provided by the data sources, that are integrated. In the temporal database research area, a bitemporal database is a database supporting valid time and transaction time. Valid time is the time when the fact is true in the modeled reality, while transaction time is the time when the fact is stored in the database. Defining a data warehouse as a bitemporal database containing integrated and subject-oriented data in support of the decision making process, transaction time in the data warehouse can always be obtained, because it is internal to a given storage system. When an event is loaded into the data warehouse, its valid time is transformed into a bitemporal element, adding transaction time, generated by the database management system of the data warehouse. However, depending on whether the data sources manage transaction time and valid time or not, we could obtain the valid time for the data warehouse or not. The aim of this paper is to present a temporal study of the different kinds of data sources to load a corporate data warehouse, using a bitemporal storage structure.

• Alberto Abelló, Elena Rodríguez, Fèlix Saltor, Marta Oliva, Cecilia Delgado, Eladio Garví and José Samos. On Operations to Conform Object-Oriented Schemas. Long paper in International Conference on Enterprise Information Systems (ICEIS 2003). Angers (France). April, 2003. Selected among the best papers of the conference to be published in "Enterprise Information Systems V", Kluwer Academic Publishers, 2004. Pages 49-56. ISBN 1-4020-1726-X
  
  

  To build a Cooperative Information System from several preexisting, heterogeneous systems, the schemas of these systems must be integrated. Operations used for this purpose include conforming operations, which change the form of a schema. In this paper we present a systematic approach to establish which conforming operations for Object-Oriented schemas are needed, and which of them can be considered as primitive, all others being derivable from these. We organize these operations in matrixes according to the Object-Oriented dimensions -Generalization/Specialization, Aggregation/Decomposition- on which they operate.

• Alberto Abelló, and Carme Martín. A Bitemporal Storage Structure for a Corporate Data Warehouse. Short paper in International Conference on Enterprise Information Systems (ICEIS 2003). Angers (France). April, 2003.
  
  

  This paper brings together two research areas, i.e. "Data Warehouses" and "Temporal Databases", involving representation of time. Looking at temporal aspects within a data warehouse, more similarities than differences between temporal databases and data warehouses have been found. The first closeness between these areas consists in the possibility of a data warehouse redefinition in terms of a bitemporal database. A bitemporal storage mechanism is proposed along this paper. In order to meet this goal, a temporal study of data sources is developed. Moreover, we will show how Object-Oriented temporal data models contribute to add the integration and subject-orientation that is required by a data warehouse.

• Alberto Abelló, Francisco Araque, Cecilia Delgado, Eladio Garví, Marta Oliva, Elena Rodríguez, Emilia Ruíz, Fèlix Saltor, José Samos, and Manolo Torres. Operaciones para Conformar Esquemas Orientados a Objetos. In Taller sobre Integración Semántica de Fuentes de Datos Distribuidas y Heterogéneas de las Jornadas de Ingeniería del Software y Bases de Datos (JISBD2002). El Escorial (Spain), November 2002. (In Spanish)
  
• Alberto Abelló, José Samos, and Fèlix Saltor. On Relationships Offering New Drill-across Possibilities (© ACM). In 5th International Workshop on Data Warehousing and OLAP (DOLAP 2002). McLean (USA), November 2002. Pages 7-13. ACM Press, 2002. ISBN 1-58113-590-4.
  
  

  OLAP tools divide concepts based on whether they are used as analysis dimensions, or are the fact subject of analysis, which gives rise to star shape schemas. Operations are always provided to navigate inside such star schemas. However, the navigation among different stars is usually overlooked. This paper studies different kinds of Object-Oriented conceptual relationships (part of UML standard) between stars (namely Derivation, Generalization, Association, and Flow) that allow to drill across them.

• Carme Martín, and Alberto Abelló. The Data Warehouse: A Temporal Database. Technical Report LSI-02-66-R. Dept Llenguatges i Sistemes Informàtics (Universitat Politècnica de Catalunya), Novembre 2002.
  
  

  Extended version of the homonimous paper published in 2003.

• Alberto Abelló, José Samos, and Fèlix Saltor. YAM² (Yet Another Multidimensional Model): An extension of UML (© IEEE). In International Database Engineering & Applications Symposium (IDEAS'02). Edmonton (Canada), July 2002. Pages 172-181. Mario A. Nascimento, M. Tamer Özsu, Osmar Zaïne Editors. IEEE Computer Society Press, 2002. ISBN 0-7695-1638-6. ISSN 1098-8086.
  
  

  This paper presents a multidimensional conceptual Object-Oriented model, its structures, integrity constraints and query operations. It has been developed as an extension of UML core metaclasses to facilitate its usage, as well as to avoid the introduction of completely new concepts. YAM² allows the representation of several semantically related star schemas, as well as summarizability and identification constraints.

• Alberto Abelló. YAM²: A Multidimensional Conceptual Model. PhD Thesis, Universitat Politècnica de Catalunya. Barcelona, April 2002.
  
  

  This thesis proposes YAM², a multidimensional conceptual model for OLAP (On-Line Analytical Processing). It is defined as an extension of UML (Unified Modeling Language). The aim is to benefit from Object-Oriented concepts and relationships to allow the definition of semantically rich multi-star schemas. Thus, the usage of Generalization, Association, Derivation, and Flow relationships (in UML terminology) is studied.
  
  An architecture based on different levels of schemas is proposed and the characteristics of its different levels defined. The benefits of this architecture are twofold. Firstly, it relates Federated Information Systems with Data Warehousing, so that advances in one area can also be used in the other. Moreover, the Data Mart schemas are defined so that they can be implemented on different Database Management Systems, while still offering a common integrated vision that allows to navigate through the different stars.
  
  The main concepts of any multidimensional model are facts and dimensions. Both are analyzed separately, based on the assumption that relationships between aggregation levels are part-whole (or composition) relationships. Thus, mereology axioms are used on that analysis to prove some properties.
  
  Besides structures, operations and integrity constraints are also defined for YAM². Due to the fact that, in this thesis, a data cube is defined as a function, operations (i.e. Drill-across, ChangeBase, Roll-up, Projection, and Selection) are defined over functions. Regarding the set of integrity constraints, they reflect the importance of summarizability (or aggregability) of measures, and pay special attention to it.
  

• Alberto Abelló, Francisco Araque, José Samos, and Fèlix Saltor. Bases de Datos Federadas, Almacenes de Datos y Análisis Multidimensional. In Taller de Almacenes de Datos y Tecnologia OLAP de las Jornadas de Ingeniería del Software y Bases de Datos (JISBD2001). Almagro (Spain), November 2001. (In Spanish)
  
• Alberto Abelló, José Samos, and Fèlix Saltor. Understanding Facts in a Multidimensional Object-Oriented Model (© ACM). In 4th International Workshop on Data Warehousing and OLAP (DOLAP 2001). Atlanta (USA), November 2001. Pages 32-39. ACM Press, 2001. ISBN 1-58113-437-1.
  
  

  "On-Line Analytical Processing" tools are used to extract information from the "Data Warehouse" in order to help in the decision making process. These tools are based on multidimensional concepts, i.e. facts and dimensions. In this paper we study the meaning of facts, and the dependencies in multidimensional data. This study is used to find relationships between cubes (in an Object-Oriented framework) and explain navigation operations.

• Alberto Abelló, José Samos, and Fèlix Saltor. Multi-star Conceptual Schemas for OLAP Systems.. Technical Report LSI-01-45-R. Dept Llenguatges i Sistemes Informàtics (Universitat Politècnica de Catalunya), October 2001.
  
  

  Extended version of the paper published in 2002: "On Relationships Offering New Drill-across Possibilities".

• Alberto Abelló, José Samos, and Fèlix Saltor. YAM2 (Yet Another Multidimensional Model): An extension of UML.. Technical Report LSI-01-43-R. Dept Llenguatges i Sistemes Informàtics (Universitat Politècnica de Catalunya), October 2001.
  
  

  Extended version of the homonimous paper published in 2002.

• Elena Rodríguez, Alberto Abelló, Marta Oliva, Fèlix Saltor, Cecilia Delgado, Eladio Garví and José Samos. On Operations along the Generalization/Specialization Dimension. In Proc. of the Int. Workshop on Engineering Federated Information Systems (EFIS 2001). Berlin (Germany), October 2001. Pages 70-83. ISBN 3-89838-027-0
  
  

  The need to derive a database schema from one or more existing schemas arises in Federated Database Systems as well as in other contexts. Operations used for this purpose include conforming operations, which change the form of a schema. In this paper we present a systematic approach to establish a set of primitive conforming operations that operate along the Generalization/Specialization dimension in the context of Object-Oriented schemas.

• Alberto Abelló, José Samos, and Fèlix Saltor. A Framework for the Classification and Description of Multidimensional Data Models (© Springer-Verlag). In 12th International Conference on Database and Expert Systems Applications (DEXA 2001). Munich (Germany), September 2001. Pages 668-677, Lecture Notes in Computer Science volume 2113. Springer, 2001. ISSN 0302-9743, ISBN 3-540-42527-6.
  
  

  The words On-Line Analytical Processing bring together a set of tools, that use multidimensional modeling in the management of information to improve the decision making process. Lately, a lot of work has been devoted to modeling the multidimensional space. The aim of this paper is twofold. On one hand, it compiles and classifies some of that work, with regard to the design phase they are used in. On the other hand, it allows to compare the different terminology used by each author, by placing all the terms in a common framework.

• Alberto Abelló, José Samos, and Fèlix Saltor. Understanding Analysis Dimensions in a Multidimensional Object-Oriented Model. In 3rd International Workshop on Design and Management of Data Warehouses (DMDW'2001). Interlaken (Switzerland), June 2001. SwissLife, ISSN 1424-4691.
  
  

  OLAP defines a set of data warehousing query tools characterized by providing a multidimensional view of data. Information can be shown at different aggregation levels (often called granularities) for each dimension. In this paper, we try to outline the benefits of understanding the relationships between those aggregation levels as Part-Whole relationships, and how it helps to address some semantic problems. Moreover, we propose the usage of other Object-Oriented constructs to keep as much semantics as possible in analysis dimensions.

• Alberto Abelló, José Samos, and Fèlix Saltor. A Data Warehouse Multidimensional Data Models Classification. Technical Report LSI-2000-6. Dept. Llenguages y Sistemas Informáticos (Universidad de Granada), December 2000.
  
  

  The words On-Line Analytical Processing (OLAP) bring together a set of tools, that use multidimensional modeling in the extraction of information from the Data Warehouse. Lately, a lot of work has been devoted to modeling the multidimensional space. The aim of this paper is twofold. On one hand, it compiles and classifies most of that work. On the other hand, it allows to compare the different terminology used by each author, by placing all the terms in a common framework.

• Elena Rodríguez, Alberto Abelló, and Marta Oliva. Resumen del Simposium en Objetos y Bases de Datos del ECOOP'2000. In Taller de Bases de Datos Orientadas a Objetos dentro de las Jornadas de Ingeniería del Software y Bases de Datos (JISBD2000). Valladolid (Spain), November 2000. (In Spanish)
  
  
• Alberto Abelló, and Elena Rodríguez. Describing BLOOM99 with regard to UML Semantics. In Proceedings of Jornadas de Ingeniería del Software y Bases de Datos (JISBD2000). Valladolid (Spain), November 2000. Pages 307-319. Gráficas Andrés Martín S.L., ISBN 84-8448-065-8.
  
  

  In this paper, we describe the BLOOM metaclasses with regard to the Unified Modeling Language (UML) semantics. We concentrate essentially on the Generalization/Specialization and Aggregation/Decomposition dimensions, because they are used to guide the integration process BLOOM was intended for. Here we focus on conceptual data modeling constructs that UML offers. In spite of UML provides much more abstractions than BLOOM, we will show that BLOOM still has some abstractions that UML does not. For some of these abstractions, we will sketch how UML can be extended to deal with this semantics that BLOOM adds.

• Fèlix Saltor, Marta Oliva, Alberto Abelló, and José Samos. Building Secure Data Warehouse Schemas from Federated Information Systems. In Int. CODATA Conference on Data and Information for the Coming Knowledge Milenium (CODATA2000), Baveno (Italy), October 2000 (Extended abstract). Heterogeneous Information Exchange and Organizational Hubs, pages 123-134. Bestougeff, Dubois and Thuraisingham Editors. Kluwer Academic Publishers, 2002. ISBN: 1-4020-0649-7.
  
  

  There are similarities between architectures for Federated Information Systems and architectures for Data Warehousing. In the context of an integrated architecture for both Federated Information Systems and Data Warehousing, we discuss how additional schema levels provide security, and operations to convert from one level to the next.

• Alberto Abelló, José Samos, and Fèlix Saltor. Benefits of an Object-Oriented Multidimensional Data Model (© Springer-Verlag). In Objects and Databases - International Symposium- in 14th European Conference on Object-Oriented Programming (ECOOP 2000). Sophia Antipolis and Cannes (France), June 2000. Pages 141-152, Lecture Notes in Computer Science volume 1944. Springer, 2000. ISSN 0302-9743, ISBN 3-540-41664-1.
  
  

  In this paper, we try to outline the goodness of using an O-O model on designing multidimensional Data Marts. We argue that multidimensional modeling is lacking in semantics, which can be obtained by using the O-O paradigm. Some benefits that could be obtained by doing this are classified in six O-O-Dimensions (i.e. Classification/Instantiation, Generalization/Specialization, Aggregation/Decomposition, Caller/Called, Derivability, and Dynamicity), and exemplified with specific cases.

• Alberto Abelló, Marta Oliva, José Samos, and Fèlix Saltor. Information System Architecture for Data Warehousing from a Federation. In Proc. of the Int. Workshop on Engineering Federated Information Systems (EFIS 2000). Dublin (Ireland), June 2000. Pages 33-40, IOS Press. ISBN 1-58603-075-2
  
  

  This paper is devoted to Data Warehousing architecture and its data schemas. We relate a federated databases architecture to Data Warehouse schemas, which allows us to provide better understanding to the characteristics of every schema, as well as the way they should be defined. Because of the confidentiality of data used to make decisions, and the federated architecture used, we also pay attention to data protection.

• Alberto Abelló, Marta Oliva, José Samos, and Fèlix Saltor. Information System Architecture for Secure Data Warehousing. Technical Report LSI-00-26-R. Dept Llenguatges i Sistemes Informàtics (Universitat Politècnica de Catalunya), April 2000.
  
  

  Extended version of the previous paper: "Information System Architecture for Data Warehousing from a Federation".

• José Samos, Alberto Abelló, Marta Oliva, Elena Rodríguez, Fèlix Saltor, Jaume Sistac, Francisco Araque, Cecilia Delgado, Eladio Garví and Emilia Ruíz. Sistema Cooperativo para la Integración de Fuentes Heterogéneas de Información y Almacenes de Datos. In Novatica, 142 (Nov-Dec 1999), pages 44-49. Asociación de Técnicos de Informática (ATI), 1999. (In Spanish). ISSN: 0211-2124.
  
  

  En este trabajo se presenta nuestra propuesta de creación de un prototipo de sistema cooperativo para la integración de fuentes heterogéneas de información y almacenes de datos en el cual se centran actualmente nuestras investigaciones. El objetivo general es proporcionar una capa de software que permita la cooperación entre diversas fuentes de información que están interconectadas mediante una red de líneas de comunicación. Cada fuente posee sus propios servicios de respuesta a preguntas que sobre sus datos realizan sus usuarios y, adicionalmente, se desea ofrecer a determinados usuarios la capacidad de acceder al conjunto de datos de una forma uniforme (acceso integrado), ya sea en tiempo real, ya sea a través de almacenes de datos.

• Alberto Abelló, Marta Oliva, Elena Rodríguez, and Fèlix Saltor. The syntax of BLOOM99 schemas. Technical Report LSI-99-34-R. Dept Llenguatges i Sistemes Informàtics (Universitat Politècnica de Catalunya), July 1999.
  
  

  The BLOOM (BarceLona Object Oriented Model) data model was developed to be the Canonical Data Model (CDM) of a Federated Database Management System prototype. Its design satisfies the features that a data model should have to be suitable as a CDM. The initial version of the model (BLOOM91) has evolved into the present version, BLOOM99.
  
  This report specifies the syntax of the schema definition language of BLOOM99. In our model, a schema is a set of classes, related through two dimensions: the generalization/specialization dimension, and the aggregation/decomposition dimension. BLOOM supports several features in each of these dimensions, through their corresponding metaclasses.
  
  Even if users are supposed to define and modify schemas in an interactive way, using a Graphical User Interface, a linear schema definition language is clearly needed. Syntax diagrams are used in this report to specify the language; an alternative using grammar productions appears as Appendix A. A possible graphical notation is given in Appendix B.
  
  A comprehensive running example illustrates the model, the language and its syntax, and the graphical notation.
  

• Alberto Abelló, Marta Oliva, Elena Rodríguez, and Fèlix Saltor. The BLOOM model revisited: An evolution proposal (poster sesion). In Workshop Reader of the 13th European Conference on Object-Oriented Programming (ECOOP'99). Lisboa, June 1999. Pages 376-378, Springer-Verlag, Lecture Notes in Computer Science. Vol. 1743, Springer, 2000. ISBN 3-540-66954-X
  
  

  Once argued the desirable characteristics of a suitable CDM, the BLOOM model (BarceLona Object Oriented Model) was progressively defined. It results in an extension of an object oriented model with a semantically rich set of abstractions. BLOOM was not developed as a whole but suffered extensions in different phases. Its abstractions were conceived for building the FDBS in as needed basis. It drove to a lack of unity and differences in the nomenclature.
  
  The necessity of revising the BLOOM model outcropped during the design process of the directory of the FDBS. It is essential to have such storage system because of the amount of needed information in building and operating a FDBS. The directory is the core of our FDBS architecture and it must contain the different schema levels as well as the mappings among them. Therefore, the model had to be fixed in order to store those schemas and mappings in a structured manner.

• Alberto Abelló. CORBA: A middleware for an heterogeneous cooperative system. Technical Report LSI-99-21-R. Dept Llenguatges i Sistemes Informàtics (Universitat Politècnica de Catalunya), May 1999.
  
  

  Two kinds of heterogeneities interfere with the integration of different information sources, those in systems and those in semantics. They generate different problems and require different solutions. This paper tries to separate them by proposing the usage of a distinct tool for each one (i.e. CORBA and BLOOM respectively), and analizing how they could collaborate. CORBA offers lots of ways to deal with distributed objects and their potential needs, while BLOOM takes care of the semantic heterogeneities. Therefore, it seems promising to handle the system heterogeneities by wrapping the components of the BLOOM execution architecture into CORBA objects.

• Alberto Abelló, and Fèlix Saltor. Implementation of the BLOOM data model on ObjectStore. Technical Report LSI-99-7-T. Dept Llenguatges i Sistemes Informàtics (Universitat Politècnica de Catalunya), May 1999.
  
  

  BLOOM is a semantically enriched object oriented data model. It offers extra semantic abstractions to better represent the real world. Those abstractions are not implemented in any commercial product. This paper explains how all them could be simulated with a software layer on an object oriented database management system. Concretely, it proved to work on ObjectStore.

• Alberto Abelló, Benet Càmpderrich, Marta Oliva, Elena Rodríguez, Fèlix Saltor, José Samos, and Jaume Sistac. El proyecto BLOOM: Bases de Datos Federadas, Interoperables y Cooperativas. In Encuentro de Investigadores en Software del Nordeste Ibérico (EncISO), Enciso (Spain), September 1998. (In Spanish)