Nowadays, databases play a key role on the dissemination and sharing of information among users throughout client-applications residing elsewhere on the network. Recently, given the success of the Internet, the number of data-centric applications and the data/traffic on the network has increased enormously resulting in a high latency in accessing data sources.

This work proposes a model that tries to minimise the data communications and latency between applications and data sources, such as databases. The model is based on the idea of employing a cache to keep results of previous queries to data sources in order to speedup future data accesses. The cache is kept within the application itself or/and within a proxy. The coherency of the data stored in the cache is maintained by the use of update or invalidate protocols. This model has been implemented as the system Polites.

The Polites is a middleware that interfaces the user applications with data sources. It has been structured in such a way that allows applications to access several types of data sources in a transparently.

Another component of this work consisted in the development of an API, named DBase, that maps the results of database queries in data structures in the TCL language. It is also responsible for keeping the content of these structures synchronized with the corresponding data whithin the mapped databases.

Polites was throughly tested and the results obtained indicate that, in certain conditions, it is able to reduce the latency and network traffic (due to the communications between applications and databases) to less than half of the initial value. However, the Polites was not found very helpful when the frequency of changes in the data being cached is too high.