In the real world, what might be a situation where it is preferable for the data for form a relation but not a function?
All I found was Edgar Cobb who invented the relational module while working at IBM in the late 1960's. Am I on the right track? Help?
When might a reversal of variables be useful in the real world?
I'm not sure but I think converting Fairenheit to Celcius is useful for this.
First, you need to know what is the difference between a relation and a function.
A relation from a set A to a set B is a subset of AxB( Cartersion product). A function from a set A to a set B is a relation from A to B such that
(1) for every a in A, ...
Real world applications for relations, functions and reversal of variables are discussed.