Hi Steve,
I agree that the target of OGC is not necessarily the "development of a single,
definitive standard ».
However the other extreme position of "bringing everything in and letting the
market decide" obviously leads to lack of interoperability, especially across
communities...
I would like to point out that yes KML came in OGC although overlapping with
GML, but that ESRI binary shapefile format did not. Perhaps OGC was more pure
at the time...
If we as spec designers don't start rationalizing among these many
possibilities, then who will?
Wouldn't you gain in getting more active in OGC standard groups that try to
address the same issues as NetCDF before making up your mind??
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 <http://www.spotimage.com>
Before printing, think about the environment
________________________________
De : Steve Hankin [mailto:Steven.C.Hankin@xxxxxxxx]
Envoyé : vendredi 21 août 2009 20:02
À : Robin, Alexandre
Cc : Tom Whittaker; Ben Domenico; Unidata GALEON; wcs-2.0.swg
Objet : Re: [galeon] [WCS-2.0.swg] CF-netCDF standards initiatives
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 <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>
<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>
<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
