Unifying Class-Based Representation Formalisms

The notion of class is ubiquitous in computer science and is central in many formalisms for the representation of structured knowledge used both in knowledge representation and in databases. In this paper we study the basic issues underlying such representation formalisms and single out both their common characteristics and their distinguishing features. Such investigation leads us to propose a unifying framework in which we are able to capture the fundamental aspects of several representation languages used in different contexts. The proposed formalism is expressed in the style of description logics, which have been introduced in knowledge representation as a means to provide a semantically well-founded basis for the structural aspects of knowledge representation systems. The description logic considered in this paper is a subset of first order logic with nice computational characteristics. It is quite expressive and features a novel combination of constructs that has not been studied before. The distinguishing constructs are number restrictions, which generalize existence and functional dependencies, inverse roles, which allow one to refer to the inverse of a relationship, and possibly cyclic assertions, which are necessary for capturing real world domains. We are able to show that it is precisely such combination of constructs that makes our logic powerful enough to model the essential set of features for defining class structures that are common to frame systems, object-oriented database languages, and semantic data models. As a consequence of the established correspondences, several significant extensions of each of the above formalisms become available. The high expressiveness of the logic we propose and the need for capturing the reasoning in different contexts forces us to distinguish between unrestricted and finite model reasoning. A notable feature of our proposal is that reasoning in both cases is decidable. We argue that, by virtue of the high expressive power and of the associated reasoning capabilities on both unrestricted and finite models, our logic provides a common core for class-based representation formalisms

Interoperabilidad entre lenguajes de modelado conceptual en crowd

Esta línea de investigación se desarrolla en forma colaborativa entre docentesinvestigadores de la Universidad Nacional del Comahue y de la Universidad Nacional del Sur, en el marco de proyectos de investigación financiados por las universidades antes mencionadas. El objetivo general del trabajo de investigación es desarrollar una nueva versión de la herramienta Web crowd, que permita la interoperabilidad de los lenguajes de modelado conceptual UML, EER y ORM, a partir de un metamodelo de unificación. Se pretende trabajar también en el soporte gráfico para sendos lenguajes, favoreciendo la comunicación entre usuarios mediante el uso de lenguajes comunes entre ellos. Como trabajo futuro, planeamos extender la codificación actual de la herramienta, basada en Lógicas Descriptivas, para una validación intra- e inter-lenguajes.Eje: Innovación en Sistemas de Software.Red de Universidades con Carreras en Informática (RedUNCI

A cookbook for temporal conceptual data modelling with description logic

We design temporal description logics suitable for reasoning about temporal conceptual data models and investigate their computational complexity. Our formalisms are based on DL-Lite logics with three types of concept inclusions (ranging from atomic concept inclusions and disjointness to the full Booleans), as well as cardinality constraints and role inclusions. In the temporal dimension, they capture future and past temporal operators on concepts, flexible and rigid roles, the operators `always' and `some time' on roles, data assertions for particular moments of time and global concept inclusions. The logics are interpreted over the Cartesian products of object domains and the flow of time (Z,<), satisfying the constant domain assumption. We prove that the most expressive of our temporal description logics (which can capture lifespan cardinalities and either qualitative or quantitative evolution constraints) turn out to be undecidable. However, by omitting some of the temporal operators on concepts/roles or by restricting the form of concept inclusions we obtain logics whose complexity ranges between PSpace and NLogSpace. These positive results were obtained by reduction to various clausal fragments of propositional temporal logic, which opens a way to employ propositional or first-order temporal provers for reasoning about temporal data models

Evolving Objects in Temporal Information Systems

This paper presents a semantic foundation of temporal conceptual models used to design temporal information systems. We consider a modelling language able to express both timestamping and evolution constraints. We conduct a deeper investigation of evolution constraints, eventually devising a model-theoretic semantics for a full-fledged model with both timestamping and evolution constraints. The proposed formalization is meant both to clarify the meaning of the various temporal constructors that appeared in the literature and to give a rigorous definition, in the context of temporal information systems, to notions like satisfiability, subsumption and logical implication. Furthermore, we show how to express temporal constraints using a subset of first-order temporal logic, i.e. DLRUS, the description logic DLR extended with the temporal operators Since and Until. We show how DLRUS is able to capture the various modelling constraints in a succinct way and to perform automated reasoning on temporal conceptual models

Evidence-based lean logic profiles for conceptual data modelling languages

Multiple logic-based reconstruction of conceptual data modelling languages such as EER, UML Class Diagrams, and ORM exists. They mainly cover various fragments of the languages and none are formalised such that the logic applies simultaneously for all three modelling language families as unifying mechanism. This hampers interchangeability, interoperability, and tooling support. In addition, due to the lack of a systematic design process of the logic used for the formalisation, hidden choices permeate the formalisations that have rendered them incompatible. We aim to address these problems, first, by structuring the logic design process in a methodological way. We generalise and extend the DSL design process to apply to logic language design more generally and, in particular, by incorporating an ontological analysis of language features in the process. Second, availing of this extended process, of evidence gathered of language feature usage, and of computational complexity insights from Description Logics (DL), we specify logic profiles taking into account the ontological commitments embedded in the languages. The profiles characterise the minimum logic structure needed to handle the semantics of conceptual models, enabling the development of interoperability tools. There is no known DL language that matches exactly the features of those profiles and the common core is small (in the tractable ALNI). Although hardly any inconsistencies can be derived with the profiles, it is promising for scalable runtime use of conceptual data models

Lenguajes austeros de modelado conceptual de datos basados en evidencias

Multiple logic-based reconstructions of UML class diagram, Entity Relationship diagrams, and Obect-Role Model diagrams exists. They mainly cover various fragments of these Conceptual Data Modelling Languages and none are formalised such that the logic applies simultaneously for the three language families as a unifying mechanism. This hampers interchangeability, interoperability, and tooling support. In addition, due to the lack of a systematic design process of the logic used for the formalisation, hidden choices permeate the formalisations that have rendered them incompatible. We aim to address these problems, first, by structuring the logic design process in a methodological way. We generalise and extend the DSL design process to logic language design. In particular, a new phase of ontological analysis of language features is included, to apply to logic language design more generally and, in particular, by incorporating an ontological analysis of language features in the process. Second, we specify minimal logic profiles availing of this extended process, including the ontological commitments embedded in the languages, of evidence gathered of language feature usage, and of computational complexity insights from Description Logics (DL). The profiles characterise the essential logic structure needed to handle the semantics of conceptual models, therewith enabling the development of interoperability tools. No known DL language matches exactly the features of those profiles and the common core is in the tractable DL ACJfl. Although hardly any inconsistencies can be derived with the profiles, it is promising for scalable runtime use of conceptual data models.Existen varias reconstrucciones basadas en lógica de lenguajes de modelado conceptual como EER, diagramas de clases UML y ORM. Principalmente cubren fragmentos de estos lenguajes, y sus formalizaciones no están hechas para que se apliquen simultáneamente a estas tres familias de lenguajes como un mecanismo de unificación. Este hecho atenta contra el intercambio y la interoperabilidad de los modelos y el desarrollo de herramientas de soporte. Además, dada la falta de un proceso sistemático de diseño, ciertas decisiones ocultas en la representación lógica hacen que las formalizaciones sean incompatibles. En este trabajo nos proponemos atacar este problema, proponiendo primero un proceso de diseño lógico que puede ser aplicado en forma metodológica. Se generaliza y extiende el proceso DSL para que se pueda aplicar al diseño de lenguajes lógicos en general, incorporando análisis ontológico de las características del lenguaje. Segundo, se especifican perfiles lógicos minimales que sacan provecho de este proceso extendido, incluyendo los compromisos ontológicos asumidos, de evidencia de uso de las características del lenguaje, y de los propiedades computacionales de las Lógicas Descriptivas (DL, description logics). Estos perfiles caracterizan la estructura lógica esencial que se necesita para manejar la semántica de los modelos conceptuales, habilitando el desarrollo de herramientas automáticas de interoperabilidad. No existe correspondencia exacta directa entre estos perfiles y fragmentos conocidos de lenguajes DL, y el núcleo común es pequeño (la lógica tratable ACNT). Aunque es muy poca la posibilidad de derivar inconsistencias dentro de estos perfiles, es prometedor su uso en modelos conceptuales dado su complejidad en tiempo escalable.Facultad de Informátic

Information management in work organization domain in network organizations

Tese de mestrado. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 200