Abstract: The process and architecture for database query processing includes techniques allowing a query to be made of various heterogeneous data sources by a client application using an adapter device specific to each source. The client application or client transmits a query received by the adapter device of the corresponding source to which the query is directed. The adapter device or adapter provides an internal representation of the query. The internal representation is then used to rewrite the query in a format compatible with the source. The rewritten or converted query is then transmitted to the data source with production of a filter object and initialisation of at least one filter chain. The filter object retrieves the results and filters the results through the filter chain. An answer object is produced to transfer results from a result conversion module to the client.