Traditionally, database applications have relied on Data Definition
Languages ( DDLs ) for the declaration of data types and Data Manipulation
Languages ( DMLs ) for the insertion, retrieval, manipulation and update
of data. Such languages have generally been lacking in the computational
power necessary for most applications, and this has been obtained either
by embedding DMLs in programming languages or extending them with
computational features, or by equipping programming languages with
persistent data types. In both cases, an uneasy amalgam of the data
model and the computational model usually arises. <P>

FDL is a database language with a single model for both data and
computation. It consists of two, purely functional, complementary levels,
the object level and the meta level. Data representation, manipulation and
querying are handled at the object level, and updates at the meta level.
This paper outlines the motivation for the development of FDL and overviews
its central features. The expressiveness and computational power furnished
by its functional model are demonstrated, and an implementation is described. <P>

Section 1 gives an overview of the Functional Data Model and of the class of
functional programming languages, both of which heavily influenced the
nature of FDL.  Section 2 introduces FDL, at the user level and at the meta
level.  Its computational power and expressiveness of query formulation are
demonstrated in Section 3.  Section 4 outlines the declaration and
enforcement of semantic integrity constraints and the modular implementation
is described in Section 5. <P>