Abstract:
A data integration system provides a uniform interface to distributed and heterogeneous sources and that provides users with transparent access this sources .A main problem of data integration is the treatment of conflicts caused by different modeling of real world entities, different data models or simply by different representations of one and the same object. This problem consists in providing a uniform view of these data sources. Several mediation systems were developed to resolve integration of heterogeneous information source.
The main objective of this research to investigate these mediation systems such as (TSIMMI , MIX , MOIMS, E-XML SIMS) , provide a comprehensive comparison between them based on the common feature these comparisons including approaches for the data integration, approach to data modeling, query languages, data source, integration model and internal and external representation and evaluate the results. The results of the comparisons between mediation systems, to observe that most of mediation used the GAV for approach to data source modeling .However the virtual approach is used by different mediation systems in approach to data integration. the data model is the core of data integration with regard all mediation systems used different model, but all of them are object-oriented models and the XML is the best data model because it is simple due to flexibility of xml to represent structured and semi-structured Information and easy to convert any data to xml. With the regards query language may differ from one data integration system to another. The researchers often choose a query language corresponding to the data model. On the other hand, data sources in mediation system are structure and semi-structure, the internal representation most of mediation system used relational database except MIX system used XML while the external representation most of mediation systems used semi-structured except MIX system is structured. Furthermore, Both GAV and LAV have some drawbacks that overcome by GLAV but most the mediation system used GAV.
