Assiging the Inventory Organization classification to the Projects owning Organizations

Hi,

I would like to know what is the eseence of assigning the inventory organization classfication while defining the Project Owning organizations.

Is it mandatory? If yes why?

We have 9 locations which are defined as Projects Organizations with the classfications as

a)Project Expenditure/Event Organization

b)Project Invoice Collection Organization

c)Project Task Owning Organization

Not worried about the above classifications but really want to understand the assignment of inventory organization classfication assignment.

Thanks

Naresh