Thx for replies so far.
5milesbaby
I'm not after any particular response. I know what I mean when I give the clearance, but recent experience has shown me that pilots don't necessarily understand the same thing.
notsofantastic
I understand your point re: speed, but if the desired speed profile is affected by a given descent rate would you be happy to make the sacrifice in order to stick to the restriction, and if not would you inform atc of your unwillingness/inability to keep the restriction? Would you assume that an average ROD would suffice?