HI Borchert,

       In OpenERP it is allowed to tag products either under the parent categories and the child categories.

So in you scenario you can tag products to machine category as well as Bran A/Bran B and no need of creating

extra categories. 

But if I wanted to associate a pricelist to the machines that are NOT brand A or brand B and are categrized as the parent which is Machine, would a pricelist rule include the children of the parent?  

My main concern is whether I need a separate Machine Child Category of "Other" or not to be able to associate a pricelist to the other machines that don't have a brand.  Hope that makes sense....