CSW, THREDDS, GALEON 2

[Ron Lake]

Hi,



When this group says CSW, I assume you mean CSW.ebRIM?


Ron



________________________________

From: owner-galeon at unidata.ucar.edu
[mailto:owner-galeon at unidata.ucar.edu] On Behalf Of Ben Domenico
Sent: November 18, 2006 1:44 PM
To: Wenli Yang
Cc: Yonsook Enloe; Liping Di; access-geoscience at lists.nasa.gov; THREDDS
community; Unidata GALEON; John Helly
Subject: Re: CSW, THREDDS, GALEON 2



Wenli,



This issue of "granularity" or heirarchies or collections or groupings
of datasets that are alike in some way was one of the issues confronted
early in the THREDDS project.  As a result, I believe we have an
approach that works reasonably well in the THREDDS Data Server package.
The issue continues to arise in most discussions of data and metadata
collections and services.  In fact it was one of the issues discussed at
the 3rd Metadata Interoperability Conference I attended last week.  It
will be important to confront it in the context of OGC and ISO
standards.  The disadvantage of doing it in the WCS context is that one
can envision collections that might include Coverages, Features, and
Sensor Observations.  For example a collection of all the data related
to a specific event such as a severe storm, a flood, a hurricane, and so
forth.  One can create THREDDS catlogs for such "case studies."   But it
would be good to eventually have a standards-based interface for such
collections.  Perhaps the OGC CSW is not well suited to this sort of use
at present.  If so, it may be useful to consider suggesting
augmentations to CSW.  I believe there is a big advantage in that we
already have a working system. 



I plan to send a copy of this to the THREDDS and GALEON groups as well
as to John Helly who convened the Interoperability Workshop last week.



Thanks for your careful description of the issues in terms of THREDDS
catalogs and OGC CSW..



-- Ben



On 11/15/06, Wenli Yang <yang at rattler-e.gsfc.nasa.gov> wrote: 

Ben,

THREDDS deals with service/data hierarchy nicely.  However, I think that
CSW does not provide guidance/standard on how hierarchical service/data
should be presented.  When mapping a THREDDS catalog into our CSW, we
can track and record the hierarchical relationships among
data/catalogReferences and among different levels of catalog references
in our database.  We haven't fully investigated how such relationships
can be presented to a CSW client (or how a CSW client can request such
relationships).  This is certainly a very useful piece of information
and deserve further discussion.  

I have not carefully read the WCS hierarchical description part which
was primarily provided by Luc.  I think that the primary intention of
using hierarchical description in WCS capability was not to let a client
actually retrieve this the hierarchy information but was to reduce the
duplication of metadata in, and thus the size of, the capabilities
document.  Initially, it was hoped that the hierarchical information
would allow a client to retrieve a collection of data sets (coverages)
from a higher node in the hierarchy but it was decided that this would
not be specified.  Of course, a specific server implementation can still
provide such capability by declaring a collection of coverages as one
single virtual coverage.  For example, a THREDDS service reference
containing a time series collection of data sets (individual coverages)
for a specific location can be declared as one coverage with a time span
covering all the data sets.   In addition, each of the data sets in the
collection can, if needed, also be separately declared as a coverage
with time range being at a point time (or a smaller time range as
compared to that of the collection). 

Wenli

At 19:04 2006-11-12 -0500, Yonsook Enloe wrote:




Ben,



This is an important topic.  Lets discuss sometime.  The next
access-geoscience telecon is scheduled for Dec 20 th.    We could
schedule one earlier to just discuss thoughts and ideas on this&..What
do you think?




Yonsook







-----Original Message-----
From: Ben Domenico [ mailto:bendomenico at gmail.com] 
Sent: Tuesday, November 07, 2006 11:19 AM
To: Liping Di; Wenli Yang; Yonsook Enloe 
Subject: CSW, THREDDS, GALEON 2



Hi all,

You are probably already aware that I think the CSW interface to THREDDS
catalogs is a key element of GALEON Phase 2.  Our experience it Phase 1
inidicated that -- at least for the WCS installations used for that
interoperability experiment, the WCS GetCapabilities request was
inadequate to provide the information available in the hierarchical
THREDDS catalogs at sites such as: 

   http://motherlode.ucar.edu:8080/thredds/idd/models.html
   http://lead4.unidata.ucar.edu:8080/thredds/catalog/ 
   http://nomads.ncdc.noaa.gov:8085/thredds/catalog/ 

I want to introduce these issues to the GALEON team, but I am very much
interested in your thoughts on whether and how the ACCESS CSW/THREDDS
work should into the GALEON Phase 2 initiative.  Please give me your
input on this topic. 

I have been holding off on moving forward with Phase 2 until the WCS 1.1
specification is adopted near the end of the year.  But perhaps we could
keep the GALEON embers burning in the meantime with a discussion of CSW
issues. 

I am convinced this is among the most important areas for standards
evolution.  Please let me know what you think.

Thanks in advance.

-- Ben