Small THREDDS catalogs and the Proposed new specification for THREDDSS Catalogs

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


http://www.ecco-group.org/thredds/sioeccoCatalog.xml

which is displayed in my (Ingrid) interface at

http://iridl.ldeo.columbia.edu/%28http://www.ecco-group.org/thredds/sioeccoCatalog.xml%29readthredds/

or

http://iridl.ldeo.columbia.edu/SOURCES/.SIO/.ECCO/


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.

So

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