Compile time in the sense that contents of the .xsd schema are fixed as
part of the specification.
The particular techniques for connecting to the .xsd via the namespace
are carried out per the XML Schema specification.
Which is why the .xml data is published in the domain's DNS data,
whereas the .xsd is not.
Compile time for whom? When is this information created and static?
If
it is hard coded, why include this "undesirable" http reference?
Simply
use a document tag registered by IANA. Otherwise, it suggests a new
set
of definitions are outside any standards body, done at any time, where
http references will be needed to "re-compile" the program that is
expected to understand this data. This could easily evolve into every
domain offering their own "compile time" version with their own
concept
of "compile time." This is an ugly camel's nose that does not belong.