When to make a new vocabulary...

All,

This is more of a philosophical question rather than a technical
question.

I have a vocabulary that my company uses to express mortgage
transactions. As we look to move into consumer lending, this vocabulary
isn't sufficient. We don't have the markup needed to express different
types of collateral or unsecured lending. It leaves us with two options:
(1) build upon the existing vocabulary to handle the new subject matter
or (2) develop a new vocabulary to handle the new subject matter.

Consumer lending is different enough from mortgage lending that I would
prefer to develop a new vocabulary to handle it. However, other believe
strongly we should modify the existing schema.

Has anyone else grappled with this sort of question? Can you offer any
advice based on your experiences? In what cases, does it make sense to
make separate vocabularies rather than one huge one?

A-