Re: [galeon] WCS core + extensions

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The issue is that each specification (and combination of core/extension
specs) applies to both clients and servers simultaneously. That is, some
spec combination X which states "a server may offer A or B or C"
translates into "a client must be prepared to handle A and B and C".

This is the only way that a client really can upfront (ie: before a
GetCoverage response is received) decide whether it can talk to this
server or not.

This is one of our curses: Every "should" in the specification, every
"may", every "if...else" multiplies the property space.)

more inline...

Aaron Braeckel wrote:
Renamed thread per Ben's suggestion.

If a 2D client talks to a 4D server, it has to be able to detect that
the WCS is beyond its capabilities but otherwise I'm not sure that much
additional complexity is imposed on clients.  A process for describing
the dimensionality of the server is definitely important with an
N-dimensional WCS, but I think this is already largely covered by the
CRS description in the current WCS specification.  I see it as another
flexible point in the specification.  Just as the WCS does not mandate
any particular encoding format or specific CRS/data projection, it would
not mandate the dimensionality of the data.  As in cases where an
unknown CRS is in use by a WCS server, a client makes a decision about
whether it is capable of handling that WCS implementation.
The reason I see N-dimensionality as preferable to a restricted
dimensionality is that the restriction:
-forces non-2D WCS implementors to fulfill a more complicated extension,
even when simple core functionality is all that is needed
-increases the number of necessary extensions, at least with how the
current extensions are described and laid out.  Minimizing the number of
extensions seems beneficial to interoperability overall
-seems to cut the WCS functionality into groupings at a different angle
than the general coverage concept (i.e. less generalized coverage
capability)

Are there cases I am forgetting that might cause problems for 2D
implementors?

well, just think about 3-D image pyramids as the analogy to the
well-known map navigation accelerator. Also tiling gets a new quality.

-Peter



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