Gopi K. Attaluri

The CORDS multidatabase project

In virtually every organization, data are stored in a variety of ways and managed by different database and file systems. Applications requiring data from multiple sources must recognize and deal with the specifics of each data source and must also perform any necessary data integration. The objective of a multidatabase system is to provide application developers and end users with an integrated view of and a uniform interface to all the required data. The view and the interface should be independent of where the data are stored and how the data are managed. CORDS is a research project focused on distributed applications. As part of this project, we are designing and prototyping a multidatabase system. This paper provides an overview of the system architecture and describes the approaches taken in the following areas: management of catalog information, schema integration, global query optimization, (distributed) transaction management, and interactions with component data sources. The prototype system gives application developers a view of a single relational database system. Currently supported component data sources include several relational database systems, a hierarchical database system, and a network database system.

Concurrency control of large unstructured data

Current research projects and database product extensions reflect the importance of unconventional database applications (for example, document processing and computer aided design). Unconventional applications differ from the conventional ones (for example, airline reservation) in the nature of transactions and data. The transactions may be complex, long and involve human interaction. The data includes small, structured objects as well as large, unstructured objects. The unstructured objects are stored in and managed by unstructured database management systems (UDS). UDS employs coarse-granularity locking which limit the concurrency and reduce the throughput of transactions. This paper deals with this problem of coarse-granularity locking at UDS. It proposes and investigates the logical concurrency control (LCC) concept as a solution. In LCC, a software module sits on top of the UDS and offers a higher-level service. This module employs application-domain-specific fine-granularity locking to achieve high concurrency.