[Mayan EDMS: 2180] How to design relations between doc types?

[Lin Pro]

Ok,
How many ways are there to setup a relation between one to many document
types?
Example:
Document type: Customer Record (metadata: name, address, phone, SSN)
Document type: Form 100 (metadata: year, form_name)
Document type: Form 200 (metadata: year, form_name)

Now I need to relate Form 100,200 to Customer Record.
What is the most logical way to do that?
Indexes, or smart links? Cabinets?

Thank for hints with examples

Lin