Link Project with Another Project

What is the recommended method for creating an "enterprise data model" and then having multiple children projects that are on its own but references some of the objects that are in that "enterprise data model"? 

E.g., "enterprise data model" is organization-wide and could include: customer, projects and sales.

A separate "marketing data model" could be very specific to marketing team, but it references the customer, projects and sales above, but adds its own tables like leads, contacts, etc. How do we maintain that link in the model?