obsolete vs. removed from the library

[Bryan@SIERRA.STANFORD.EDU.UUCP]

Dear Ada Fans (if you're not a fan of Ada, I don't care that you read this),

I'm confused again... is there a difference between "obsolete" compilation
units and units "removed" ("deleted" for you VMS fans) from the library?
Consider:

	package P is end P;

	with P;
	procedure Q is begin null; end;

	package P is end P;

	with P;
	procedure Q is begin null; end;

The second compilation of P makes Q obsolete.  It also makes the implicit
specification of Q (which is in the library) obsolete.  Does this mean
that the second compilation of the body of Q is invalid since it is
a secondary unit of an obsolete spec?

This is related to a question I sent out a while ago, but never received
any replies to.  Are there only two library states associated with a unit,

	1. not in the library; never successfully compiled.
	2. in the library; ready to elaborate

??

Or are there three library states assocaited with a unit?

	1 - 2 as above
	3. obsolete; not ready to elaborate, but was successfully
	   compiled once

doug
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