Robin, Alexandre wrote:
Hi Steve,
Just to clarify when I said NetCDF was a "NEW standard" I meant a new
standard in OGC.
As I was telling Ben in an offline email, I am totally conscious of
its penetration and usefulness in certain communities.
However, _I am not convinced that /having two standards doing the same
thing in OGC /is sending the right message and is the best way to go
for a standardization organization_.
Hi Robin,
I confess that I was aware of using a cheap rhetorical device when I
twisted your intended meaning of "NEW". (Begging your tolerance.) It
was helpful in order to raise more fundamental questions. You have
alluded to a key question just above. Is it really best to think of the
target of OGC as a the development of a single, definitive standard? one
that is more general and more powerful than all existing standards? Or
is it better to think of OGC as a process, through which the forces of
divergence in geospatial IT systems can be weakened leading towards
convergence over time? The notion that there can be a single OGC
solution is already patently an illusion. Which one would you pick?
WFS? WCS? SOS with SWE Common? SOS with its many other XML schema?
(Lets not even look into the profusion of WFS application schema.) I
trust that we are not pinning our hopes on a future consolidation of all
of these. There is little evidence to indicate that we can sustain the
focus necessary to traverse that path. The underlying technology is not
standing still.
What Ben (and David Arctur and others) have proposed through seeking to
put an OGC stamp of approval on netCDF-CF technology is similar to what
OGC has achieved through putting its stamp on KML ("There are sound
business and policy reasons for doing so.") It is to create a process
-- a technical conversation if you will -- which will lead to
interoperability pathways that bridge technologies and communities.
Real-world interoperability.
There has been a lot of experimentation with SWE technologies as well
that you may not know about and in many communities, especially in
earth science.
What I'm saying is that perhaps it is worth testing bridging NetCDF to
SWE before we go the way of stamping two 100% overlapping standards as
OGC compliant.
Complete agreement that this sort of testing ought to occur. And
interest to hear more about what has been achieved. But great
skepticism that there is this degree of overlap between the approaches.
And disagreement that this testing ought to be a precondition to OGC
recognition of a significant ,community-proven interoperability
mechanism like netCDF. OGC standardization of netCDF will provide a
forum for testing and experimentation to occur much more rapidly and for
a 2-way transfer of the best ideas between approaches. NetCDF & co.
(its API, data model, CF, DAP) have a great deal to offer to OGC.
- Steve
Regards,
-------------------------------------------------
**Alexandre Robin**
Spot Image, Web and E-Business
Tel: +33 (0)5 62 19 43 62
Fax: +33 (0)5 62 19 43 43
http://www.spotimage.com
Before printing, think about the environment
------------------------------------------------------------------------
*De :* Steve Hankin [mailto:Steven.C.Hankin@xxxxxxxx]
*Envoyé :* jeudi 20 août 2009 20:58
*À :* Tom Whittaker
*Cc :* Robin, Alexandre; Ben Domenico; Unidata GALEON; wcs-2.0.swg
*Objet :* Re: [galeon] [WCS-2.0.swg] CF-netCDF standards initiatives
Hi Tom,
I am grateful to you for opening the door to comments "from 10
thousand feet" -- fundamental truths that we know from many years of
experience, but that we fear may be getting short shrift in
discussions of a new technology. I'd like to offer a comment of that
sort regarding the interplay of ideas today between Robin ("/I hope we
don't have to define a NEW standard .../") and Carl Reed ("/there are
other organizations interested in bringing legacy spatial encodings
into the OGC. There are sound business and policy reasons for doing
so./").
The NEW standard in this discussion is arguably SWE, rather than
netCDF. NetCDF has decades of practice behind it; huge bodies of data
based upon it; a wide range of applications capable of accessing it
(both locally and remotely); and communities that depend vitally upon
it. As Ben points out, netCDF also has its own de jure pedigree.
A key peril shared by most IT standards committees -- a lesson that
has been learned, forgotten, relearned and forgotten again so many
times that it is clearly an issue of basic human behavior -- is that
they will try to innovate. Too-common committee behavior is to
propose, discuss and document new and intriguing technologies, and
then advance those documents through a de jure standards process,
despite an insufficient level of testing. The OGC testbed process
exists to address this, but we see continually how large the gap is
between the testbed process and the pace and complexity of innovations
emerging from committees.
Excellent reading on this subject is the essay by Michi Henning, /The
Rise and Fall of CORBA/ (2006 --
http://queue.acm.org/detail.cfm?id=1142044). Among the many insights
he offers is
**'Standards consortia need iron-clad rules to ensure that they
standardize existing best practice.** There is no room for innovation
in standards_._ Throwing in "just that extra little feature"
inevitably causes unforeseen technical problems, despite the best
intentions.'
While it adds weight to an argument to be able to quote from an
in-print source, this is a self-evident truth. We need only reflect
on the recent history of IT. What we need is to work together to find
ways to prevent ourselves from continually forgetting it.
There is little question in my mind that putting an OGC stamp of
approval on netCDF is a win-win process -- for the met/ocean/climate
community and for the broader geospatial community. It will be a path
to greater interoperability in the long run and it deserves to go
forward. The merits of SWE (or GML) as an alternative approach to the
same functionality also deserve to be explored and tested in
situations of realistic complexity. But this exploration should be
understood initially as a process of R&D -- a required step before a
"standards process" is considered. If that exploration has already
been done it should be widely disseminated, discussed and evaluated.
- Steve
==================================
Tom Whittaker wrote:
I may be ignorant about these issues, so please forgive me if I am
completely out-of-line....but when I looked at the examples, I got
very concerned since the metadata needed to interpret the data values
in the "data files" is apparently not actually in the file, but
somewhere else. We've been here before: One of the single biggest
mistakes that the meteorological community made in defining a
distribution format for realtime, streaming data was BUFR -- because
the "tables" needed to interpret the contents of the files are
somewhere else....and sometimes, end users cannot find them!
NetCDF and ncML maintain the essential metadata within the files:
types, units, coordinates -- and I strongly urge you (or whomever) not
to make the "BUFR mistake" again -- put the metadata into the files!
Do not require the end user to have to have an internet connection to
simply "read" the data....many people download the files and then
"take them along" when traveling, for example.
If I simply downloaded the file at
<http://schemas.opengis.net/om/1.0.0/examples/weatherObservation.xml>
I would not be able to read it. In fact, it looks like even if I also
got the "metadata" file at:
<http://schemas.opengis.net/om/1.0.0/examples/weatherRecord1.xml>
I would still not be able to read it, since it also refers to other
servers in the universe to obtain essential metadata.
That is my 2 cents worth....and I hope I am wrong about what I saw in
the examples....
tom
