Semantic and pragmatic processing in FIDO: a flexible interface for data-base operations

This article deals with a flexible natural language interface to access data stored in a relational data base. This interface may prove of great value to the less sophisticated user. The FIDO system (Flexible Interface for Database Operations) is presented; it accepts queries issued in natural language (Italian) and translates them into relational algebra operations. FIDO is composed of a parser (not described in the paper), a two-level semantic network, which (among other things) expresses the correspondence between the natural language terms and the conceptual database objects, and a translator/optimizer, which translates the conceptual query into its logical equivalent (i.e. into a query expressed in terms of stored relations and their attributes). The article describes the main characteristics of the semantic network and addresses, in greater detail, the problem of query translation and optimization. The flexibility of FIDO is due to the complete independence of the semantic knowledge source from the logical schema of the data base. In fact, the logical schema can be designed on the basis of considerations not related to the overall structure of FIDO (e.g. the presence of particular types of applications that have to be implemented in a particularly efficient way). In principle, the (relational) data base could be preexistent with respect to the adoption of FIDO, in that the data structures used by the translator/optimizer and described in this paper are able to describe the correspondence between the conceptual model of the domain and different logical schemas.