Peter McBrien

Data integration by bi-directional schema transformation rules

We describe a new approach to data integration which subsumes the previous approaches of local as view (LAV) and global as view (GAV). Our method, which we term both as view (BAV), is based on the use of reversible schema transformation sequences. We show how LAV and GAV view definitions can be fully derived from BAV schema transformation sequences, and how BAV transformation sequences may be partially derived from LAV or GAV view definitions. We also show how BAV supports the evolution of both global and local schemas, and we discuss ongoing implementation of the BAV approach within the AutoMed project.

Schema Evolution in Heterogeneous Database Architectures, A Schema Transformation Approach

This paper presents a new approach to schema evolution, which combines the activities of schema integration and schema evolution into one framework. In previous work we have developed a general framework to support schema transformation and integration in heterogeneous database architectures. Here we show how this framework also readily supports evolution of source schemas, allowing the global schema and the query translation pathways to be easily repaired, as opposed to having to be regenerated, after changes to source schemas.

A Uniform Approach to Inter-model Transformations

Whilst it is a common task in systems integration to have to transform between different semantic data models, such inter-model transformations are often specified in an ad hoc manner. Further, they are usually based on transforming all data into one common data model, which may not contain suitable data constructs to model directly all aspects of the data models being integrated. Our approach is to define each of these data models in terms of a lower-level hypergraph-based data model. We show how such definitions can be used to automatically derive schema transformation operators for the higher-level data models. We also show how these higher-level transformations can be used to perform inter-model transformations, and to define inter-model links.

AutoMed: A BAV Data Integration System for Heterogeneous Data Sources

This paper describes the AutoMed repository and some associated tools, which provide the first implementation of the both as view (BAV) approach to data integration. Apart from being a highly expressive data integration approach, BAV in additional provides a method to support a wide range of data modelling languages, and describes transformations between those data modelling languages. This paper documents how BAV has been implemented in the AutoMed repository, and how several practical problems in data integration between heterogeneous data sources have been solved. We illustrate the implementation with examples in the relational, ER, and semi-structured data models.

A Semantic Approach to Integrating XML and Structured Data Sources

XML is fast becoming the standard for information exchange on the WWW. As such, information expressed in XML will need to be integrated with existing information systems, which are mostly based on structured data models such as relational, object-oriented or object/ relational data models. This paper shows how our previous framework for integrating heterogeneous structured data sources can also be used for integrating XML data sources with each other and/or with other structured data sources. Our framework allows constructs from multiple modelling languages to co-exist within the same intermediate schema, and allows automatic translation of data, queries and updates between semantically equivalent or overlapping heterogenous schemas.

A formalisation of semantic schema integration

Abstract Several methodologies for the semantic integration of databases have been proposed in the literature. These often use a variant of the Entity-Relationship (ER) model as the common data model. To aid the schema conforming, merging and restructuring phases of the semantic integration process, various transformations have been defined that map between ER representations which are in some sense equivalent. Our work aims to formalise the notion of schema equivalence and to provide a formal underpinning for the schema integration process. We show how transformational, mapping and behavioural schema equivalence are all variants of a more general definition of schema equivalence. We propose a semantically sound set of primitive transformations and show how they can be used to express the transformations commonly used during the schema integration process and to define new transformations. We differentiate between transformations which apply to any instance of a schema and those which require knowledge-based reasoning since they apply only for certain instances; this distinction could serve to enhance the performance of transformation tools since it identifies which transformations must be verified by inspection of the schema extension; it also serves to identify when intelligent reasoning is required during the schema integration process.

Comparing and transforming between data models via an intermediate hypergraph data model

Data integration is frequently performed between heterogeneous data sources, requiring that not only a schema, but also the data modelling language in which that schema is represented must be transformed between one data source and another. This paper describes an extension to the hypergraph data model (HDM), used in the AutoMed data integration approach, that allows constraint constructs found in static data modelling languages to be represented by a small set of primitive constraint operators in the HDM. In addition, a set of five equivalence preserving transformation rules are defined that operate over this extended HDM. These transformation rules are shown to allow a bidirectional mapping to be defined between equivalent relational, ER, UML and ORM schemas. The approach we propose provides a precise framework in which to compare data modelling languages, and precisely identifies what semantics of a particular domain one data model may express that another data model may not express. The approach also forms the platform for further work in automating the process of transforming between different data modelling languages. The use of the both-as-view approach to data integration means that a bidirectional association is produced between schemas in the data modelling language. Hence a further advantage of the approach is that composition of data mappings may be performed such that mapping two schemas to one common schema will produce a bidirectional mapping between the original two data sources.

Information systems development using a combination of process and rule based approaches

During the last years, the time aspect in information systems development has been addressed by several researchers [2], [8], [6]. Organisations are dynamic by nature and thus, the importance of modelling time explicitly in systems engineering approaches is crucial. This paper proposes a way of integrating process and rule based approaches in information systems development. Both static and dynamic aspects including the temporal dimension can be described. We envisage an approach with incremental specifications where details are successively added until we arrive at a specification from which executable code can be automatically generated. The output from this process (i.e., a set of rules) should be compatible with a rule manager which controls the execution of the system. A prototype has been developed to demonstrate the feasibility of this approach and is briefly described.

Integrating database technology, rule-based systems and temporal reasoning for effective information systems: the TEMPORA paradigm

Abstract. Recent years have witnessed a growing realization that the development of large data‐intensive, transaction‐oriented information systems is becoming increasingly more difficult as user requirements become broader and more sophisticated. Contemporary approaches have been criticized for producing systems which are difficult to maintain and which provide little assistance in organizational developments. This paper introduces the TEMPORA paradigm, which is currently under development and which advocates a closer alignment between organizational policy and information system functionality. This viewpoint impacts on a number of critical issues related to the development process of information systems most notably in the nature of conceptual models, the discipline adopted for the development, the type of support provided by CASE tools and the run‐time environment. The paper introduces the philosophy and architecture of the TEMPORA paradigm and describes the conceptual models, tools and run‐time environment which render such an approach a feasible undertaking.

A rule language to capture and model business policy specifications

The TEMPORA paradigm for the development of large data intensive, transaction oriented information systems explicitly recognises the role of organisational policy within an information system, and visibly maintains this policy throughout the software development process, from requirements specifications through to an executable implementation.