persistence of service URLs

[Robert Olson]

An issue of mild importance is the longevity of a particular service URL. 
This becomes more important if they are used as long-term identifiers, say 
for connections between venues on different servers.

This is a situation similar to the GSH/GSR distinction in OGSA; their 
solution is to define persistent names that are resolved with a mapping 
service. I'm not sure we care enough; I'm inclined to solve this 
differently for the time being.

    o	Assign a persistent port for each server we care to make
	persistently accessible.

    o	Assign a persistent service identifier for each service
	we care to make persistently accessible (instead of the
	sequentially or randomly generated service id we use
	now).

With these rules and by taking some care about when we apply them we should 
be able to have enough persistence to accomplish our task.

--bob