A publish/subscribe system is a middleware communication service that delivers messages from a sender to one or more receivers using the preferences expressed by those receivers, rather than relying on an explicit destination address set by the sender. The historical development of publish/subscribe systems has followed a line which has evolved from channel-based systems, to subject-based syste...

The interoperation of information from various data sources, internet services and applications is a central topic in scientific research. Due to the fact that today interoperation requires a high degree of user knowledge and domain expertise in order to combine services in life science applications, we need a smarter mediator-based interoperation. In particular, biologists cannot answer questi...

The previous studies about the maintenance systems were dealt with defining the evaluation criteria, grouping them, and using different techniques for evaluating. The main problem is that maintenance subsystems and the relationship between and within them in order to a reliable evaluation have never been identified before.The contribution of this study is realizing the four maintenance su...

A database mediator system combines information from multiple existing source databases and creates a new virtual, mediated database that comprises the integrated entities and their relationships. When mediating scientific data, the technically challenging problem of mediator query processing is further complicated by the complexity of the source data and the relationships between them. In part...

This thesis reports on the results of a study of the nested join operator in a mediator-based setting. As the rate at which data is accumulated increases, the need for integration of di erent (physical) Database Management Systems (DBMS) becomes apparent. The most fundamental and arguably important operation that is used in order to achieve this is the join-operator. The nested-relational model...