Ex8 Optional attribute

This forum is for discussing the development of Rel examples and sample applications.
Chris Walton
Posts:76
Joined:Sat Aug 18, 2012 2:13 pm
Ex8 Optional attribute

Post by Chris Walton » Fri Aug 16, 2013 7:05 pm

Optional attribute

Code: Select all

VAR Arbitrary BASE RELATION { name CHARACTER } KEY { name };
VAR Arbitrary_predicate BASE RELATION { name CHARACTER, predicate CHARACTER } KEY { name };
CONSTRAINT Arbitrary_predicate_opt Arbitrary_predicate { name } <= Arbitrary { name };
Notes
This is one of (probably) many ways of defining an optional attribute.

Post Reply