Small THREDDS catalogs and the Proposed new specification for THREDDSS Catalogs
- To: John Caron <address@hidden>
- Subject: Small THREDDS catalogs and the Proposed new specification for THREDDSS Catalogs
- From: Benno Blumenthal <address@hidden>
- Date: Mon, 26 Apr 2004 11:01:39 -0400
John Caron wrote:
A proposed new version of the THREDDS Dataset Inventory Catalog is
ready for your comments. Please send them to address@hidden,
or to me.I am glad to see some expansion of the spec so that we can convey more
information about our datasets. I have a question, however, about
switching from DTD to XML Schema.
My view of THREDDS DIC in general is that it allows a data provider to
describe their collection of data sets at a level of utility not
generally available. I understand there is a considerable effort to
generate catalogs automatically for existing collections, and that is
important, but I think one can provide information in the THREDDS format
that cannot be simply expressed by, for example, a collection of typed
files in a directory. So if providers have the detailed information
about their datasets, it is probably a set of links on an HTML page
(extended documentation in HTML or PDF files, perhaps links to metadata
files, etc), along with documentation for the collection as a whole.
Also, many providers only provide a few datasets. So the path of least
resistance for many is to simply write the THREDDS file.
In light of this, I have been encouraging groups to write THREDDS xml
files (version 0.6) to describe their collections. Not that I have had
a tremendous amount of success so far, but given some more time, I am
hopeful of more to show. For example, there is
which is displayed in my (Ingrid) interface at
So given the THREDDS catalog generation options, they chose to write it
by hand, and I taught them the nuances of the tags. Pretty reasonable
given the small number of datasets and the additional documentation that
we wanted to link in. I am a little embarassed that the next THREDDS
version is so different from the first, though I guess that is my
problem more that anyone elses.
1) What are the benefits of changing from DTD to XML Schema? Does it
include an automatic editing interface easily accessible to everyone?
2) Can you provide a conversion utility on the web so that anyone that
has written an old-format file can instantly get a new-format version?
If the new format is much easy to edit than the old (because interfaces
are readily available), I think the sell for switching can be made.
Otherwise, users may be annoyed, i.e. slow to switch and/or adopt.
Dr. M. Benno Blumenthal address@hidden
International Research Institute for climate prediction
The Earth Institute at Columbia University
Lamont Campus, Palisades NY 10964-8000 (845) 680-4450
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