[TYPO3-mvc] extbase: relations simple question

[Dmitri Pusarev]

Hey!
In my model I have a Client and a Project. Relations which pop into my 
mind from the business domain:
a)Client has a relation projects with Project, 0..*(fk).
b)Project has a relation client with Client, 0..1.
Should I create both a) and b)? Or just a) is enough?

In the database language(which I more used to), I would just create a 
field 'client' in the table 'Projects'.

Sorry, I'm still learning!

Cheers,
Dmitri.