Versions and configurations in object-oriented database systems : a uniform treatment

Object-oriented database models usually allow versions only at the most specialized type/c1ass in an inheritance hierarchy. The possibility of having versions at different levels of abstraction provides a richer model and allows a more natural representation of the reality. The presence of objects and its corresponding sets of versions at different levels of a type/class hierarchy introduces the need for handling version mappings. Integrity constraints can be associated to these mappings, restricting the set of possible combinations of versions appearing at different levels of the hierarchy. Sets of versions associated with each levei of an object hierarchy often represent a very large set of possible configurations for that object, which is difficult to be handled directly by the user. In this context, adequate mechanisms are very important to define and build object configurations by means of selections applied to the set of all possible configurations, defined by the combinations of versions. This paper proposes an approach in which versions and configurations may appear at different levels of an inheritance hierarchy, and a uniform treatment is given to these two concepts

A logic programming framework for modeling temporal objects

Published versio

Modeling Time from a Conceptual Perspective

Although many temporal models have been proposed in the literature, there is still need for a conceptual model capturing the essential semantics of time-varying information that is free of implementation concerns. This paper first discusses important criteria to be considered when assessing the ÒconceptualÓ quality of a temporal model. Then, it presents the main temporal features of MADS, a spatio-temporal conceptual model. The focus is on identifying issues that are either open or controversial, and discussing alternatives, if any. Finally, it is shown how the model may be implemented on top of either TSQL2 or a traditional, non-temporal data model

Spatio-Temporal Conceptual Models: Data Structures + Space + Time

Nowadays, many applications need data modeling facilities for the description of complex objects with spatial and/or temporal facilities. Responses to such requirements may be found in Geographic Information Systems (GIS), in some DBMS, or in the research literature. However, most of existing models cover only partly the requirements (they address either spatial or temporal modeling), and most are at the logical level, hence not well suited for database design. This paper proposes a spatio-temporal modeling approach at the conceptual level, called MADS. The proposal stems from the identification of the criteria to be met for a conceptual model. It is advocated that orthogonality is the key issue for achieving a powerful and intuitive conceptual model. Thus, the proposal focuses on highlighting similarities in the modeling of space and time, which enhance readability and understandability of the model

Uma abordagem multi-nivel para suporte a versoes em bancos de dados orientados a objetos

O uso de Sistemas de Bancos de Dados em aplicações não convencionais evidenciou requisitos não atendidos pelos sistemas tradicionais, motivando pesquisas em torno do Paradigma da Orientação a Objetos. Destaca-se o requisito de liberação do número de possíveis instâncias associadas a um mesmo objeto, para a representação do histórico de um objeto, ou para um tratamento flexível da evolução de esquemas, ou, ainda, para manutenção da consistência dos dados em utilização concorrente. Esta liberação conduziu ao conceito de versão. Este trabalho apresenta uma análise do conceito de versão frente aos demais conceitos já incorporados ao paradigma de orientação a objetos, discutindo a necessidade dos novos conceitos. São consideradas as relações entre versões, bem como os condicionamentos impostos pelas hierarquias de classes e tipos sobre as versões de objetos ascendentes ,e descendentes. É proposta uma arquitetura na qual é admitido o versionamento de objetos em qualquer nível da hierarquia de herança, em contraposição aos modelos que admitem apenas o versionamento nas folhas da hierarquia. É mostrado como o modelo proposto descreve com mais propriedade várias situações encontradas em aplicações.The use of Database Management Systems to support non conventional applications put in evidence a set of requirements not supported by the traditional database systerns, and strongly motivated research work towards object oriented database systems. In this context, it was evident the need to liberate the number of instances associated to one database object, to represent the history of the object, to gain flexibility in schema evolution, ar to maintain data consistency, in concurrent access environments, originating the version concept. This work presents an analysis of the version concept, when integrated with the already incorporated concepts of the object-oriented paradigm and discusses the need for new concepts. Aspects considered include: relationships between versions, as well as the conditions imposed by the class and type hierarchies over the versioning of objects and its ascendants and descendants. A multi-Ievel architecture is proposed, which allows versioned objects to appear in any levei of a type ar class hierarchy. This approach is compared with the traditional one, in which versions appear only at the leaves of the hierarchies. It is shown how the proposed architecture allows modeling of many situations of real world applications in a more natural way

Temper : uma abordagem para modelagem temporal de banco de dados

Several temporal extensions to the original entity-relationship (ER) approach have been proposed in literature. A temporal ER model includes temporal ER elements (entities, relationships and attributes). Temporal ER elements are ER elements that vary with the time. A temporal ER model describes a database that stores the history of changes of the temporal ER êlements. The temporal extensions proposed in literature have some restrictions. Some of the approaches require ali the elements of the model to be temporal, not allowing the use of temporal and not temporal elements at the same time. Other approaches use temporal intervals instead of temporal instants. The semantics of a model based on temporal intervals is more complex if compared to a model based on temporal instants, This complexity results in complex query and manipulation languages. The paper presents the two fundamental concepts in temporal modeling (temporal intervals and temporal instances), discusses temporal modeling approaches and introduces the TempER approach, a temporal modeling approach defined to overcome the identified problems.Várias extensões à abordagem entidade-relacionamento original têm sido propostas com o objetivo de incorporar a possibilidade de modelar propriedades temporais. Estas abordagens, entretanto, apresentam várias restrições. Algumas exigem que o modelo contenha. exclusivamente elementos temporalizados, não permitindo a combinação de elementos temporalizados com não temporalizados. Outras trabalham com intervalos de tempo, ao invés de pontos no tempo. Modelos baseados em intervalos de tempo, têm semântica mais complexa e tornam linguagens de consulta e manipulação mais complexas. O presente artigo apresenta os modelos fundamentais de temporalização que aparecem na literatura (intervalos de tempo e pontos de tempo), discute as abordagens para modelagem temporal existentes e apresenta a abordagem TempER, modelo de dados temporal que procura corrigir os problemas identificados nas demais abordagens