What I want to accomplish is limit the number of types of tokens in a process flow segment or zone at any given time. The zone should allow any number of tokens with the same type (or in my case OrderID) as those already in the zone to enter, but tokens with a different type should be held back until the zone is cleared of tokens with a dissimilar type.
I thought a zone would be obvious for this, but what I am trying to do is essentially to create partitions by type and limit, not the number of tokens in each partition, but the total number of partitions the zone is allowed to create.
Of course it does not have to be handled by a zone if there is a simpler way, but it just seemed like the obvious activity for the job.