An interface for user-defined functions in a database application

This paper describes a database application, which permits users to write their own functions in a limited way using a scripting language consisting of a set of canned functions written in APL. Inputs to the function can be database fields and/or constant values. This provides users with additional flexibility in generating reports and selection statements.The user must first define the function inputs and outputs assigning names, position, data types, default values and descriptions for each. Then the user writes a script in the database language, making reference to the named input and output fields. The scripting language is limited to a defined set of functions and certain ASCII symbols.A limited set of control structures are permitted, such as if-then-else, and while loops.The application consists of an editor, which allows the user to describe the inputs and write the script, and a "compiler", which generates an APL function, which behaves in a similar manner to the canned functions, provided with the database application. The "compiler" inserts data assignment and input checking into the function based on the data type and data structure permitted by the user.