The basic types of Definitions used most commonly throughout ECL
coding are: Boolean, Value, Set, Record Set, and TypeDef.
A Boolean Definition is defined as any Definition whose definition
is a logical expression resulting in a TRUE/FALSE result. For example, the
following are all Boolean Definitions:
IsBoolTrue := TRUE;
IsFloridian := Person.per_st = 'FL';
IsOldPerson := Person.Age >= 65;