[firebird-support] Primary key with negative value

[jakefeed]

We have an database in which we supply product catalogs with pricing.  The end 
user can create their own items, too. In order to separate the user's items 
from the items we supply, we're contemplating using negative primary keys for 
our items and positive primary keys for the users items.  We are using Firebird 
2.5.1.  Are there any known issues using negative primary key values in this 
configuration.  Thank you.