service type - a named mechanism for accessing scientific data
access - a (named?) binding of a URI to a specific service type
metadata type - a named convention for description of scientific data
metadata - a (named?) binding of a text fragment to a specific metadata type
metadata reference - a (named?) binding of a URI to a specific metadata type
dataset - a named collection of access objects and metadata
collection - a named collection of datasets
In contrast, the following concepts are not clearly orthogonal to me:
documentation - equivalent to metadata with a human-readable metadata type
John, hope this is useful input.
Benno Blumenthal wrote:
John Caron wrote:
Im trying to think what is the meaning of serviceType="Catalog" in
What should the client assume? It seems that if you want the client
able to get the collection as a dataset, then you add a dataset
you want the client to "drill down" further, then a collection or
element can do that. What I have removed is the clear association
the dataset element and the collection, eg that these are the same
have also made it more cumbersome(need two elements). I agree these are
The client does not know that these are two different ways of looking at the same thing -- the key piece of information that was trying to be conveyed. The client does not have to present both -- maybe the client only presents THREDDS choices because it has no DODS capabilities, another client does not present the drill-down because it does have DODS capabilities.
The fact that you can produce a dataset as COARDS vs DIF, etc is
also for me
not so great of an example. Rather than modifying the underlying
(eg DODS), it seems simpler to add a metadata element. I admit that
just an idea which has not been done yet. And you already have a
does in fact modify the data access. But think of it from a client POV.
Should she search through the services looking for a service of type
subtype COARDS? Or search through the metadata looking for COARDS
independent of service type?
My point was your metadata tag was services for metadata. clients that can only handle COARDS metadata would ask for COARDS metadata services.
A more compelling example would be where the dataset is served up
FTP and DODS, and ADDE, etc. But then I wonder/doubt whether one URL is
likely to be able to be used for all these services.
DODS already has multiple services -- ascii is not necessarily present, some of the selection interfaces are optional, metadata is optional.
> I am also concerned about XYZT clients (4D world view) -- how can I
> them against higher (and other) dimensional data (ensemble member
> spectral, different kinds of time (forecast start, lead, target
> could convert to multiple datasets, or spatial grids, but it
would be nice
> advertise the service. As well as supporting various binary and
> formats. Or the THREDDS dataset (as opposed to collection/catalog)
I am not clear of "protect", did you mean "project" ?
Protect -- 4D world clients simply fail when given something else, I would like them to have an alternative.
> 2) The access for the dataset LEVITUS94 is again via THREDDS
> collection) or via DODS (the access statement). Adding another
> the collection called "Daily" is not the same meaning at all.
Sorry, I should have had:
<dataset name="LEVITUS94 dataset" urlPath="SOURCES/.LEVITUS94/dods"/> <catalogRef xlink:title="Drill down into dataset" xlink:href="http://iridl.ldeo.columbia.edu/SOURCES/LEVITUS94/thredds.xml" />
In this case the dataset is presented to the user for immediate selection AND a link is presented for drilling further down.
This is the wrong example: LEVITUS94 was a collection that was also available through DODS -- now you have lost it completely.
It is an example for the subdatasets ANNUAL, etc, with the flaw that clients no longer can tell that these are two different ways of getting the same thing as mentioned above.
Besides, multiple services also will show up in aggregations of THREDDS catalogs -- multiple servers serving the same dataset could be represented as a single entry with multiple services -- in this case, services with identical attributes except for path information.
The main thing service does is to let you specify a type and factor
common URL base. then this is passed to "protocol aware" code.
das,dds,dods,info,ascii subservice URLs are always regular in how
formed, it seems unnecessary to actually specify them. In principle
subservices are probably useful but some concrete examples are needed.
As I mentioned earlier, not all DODS servers have all the services. Even if they did, it would not hurt to be able to list them.
While I have not given examples, different datasets will have
> services, which is why I kept specifying using the access tag. Some
> will be incompatible with certain representations, so the service
> vary. One could argue that the THREDDS standard collection is a
> available via DODS -- certainly that is the case for me.
I understand you want to compactly specify what services are available for datasets. Im not sure we have enough examples to make sure we are doing it right. I am also oriented towards incremental design, doing what we can get right and iterating.
OK with me, but we have lost the structure I was trying to express -- alternate ways of accessing the same object, with emphasis on the same object.
-- Dr. M. Benno Blumenthal address@hidden International Research Institute for climate prediction Lamont-Doherty Earth Observatory of Columbia University Palisades NY 10964-8000 (845) 680-4450
-- Joe Wielgosz address@hidden / (707)826-2631 --------------------------------------------------- Center for Ocean-Land-Atmosphere Studies (COLA) Institute for Global Environment and Society (IGES) http://www.iges.org
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