Re: orthogonality (was Re: New attempt)

I think the word dataset is causing trouble. There are at least three 
potential meanings for this word in the context of THREDDS:

1) an entity that is considered as a unit by human beings

2) an entity that can be operated on as a unit by the THREDDS API

3) an entity that can be operated on as a unit by a data access protocol

Right now, only the entities described by "access" tags meet all of 1, 
2, and 3.

The tags "dataset" and "collection" both describe entities that only 
meet 1 and 2.   Thus I agree with benno that there is not a very 
meaningful distinction between them (and reconsider my listing of them 
as orthogonal concepts in my previous message).

I wonder if it would be a good idea to merge these concepts and use a 
less loaded word, say "entry", to refer to an entity that has meaning to 
THREDDS and to end users, but not to a data access protocol, i.e.

<catalog>
<service name="X"/>
<service name="Y"/>
...

<entry name="my_dataset">

   <metadata name="global-metadata" url="..."/>
   <access name="global-X-access"/>

   <entry name="monthly-data">
     <metadata name="monthly-metadata" url="..."/>
     <access name="X-with-COARDS" serviceType="X" url="..."/>
     <access name="X-with-no-COARDS" serviceType="X" url="..."/>
     <access name="X-flattened-to-2D" serviceType="X" url="http://..."/>
     <access name="Y" serviceType="Y" url="..."/>
     ....
   </entry>


</entry>

- Joe


Daniel Holloway wrote:

> Benno Blumenthal wrote:
>
>
> > John Caron wrote:
> >
> >
> > > Much harder question is the distinction between a dataset and a
> > > collection,
> > > since a dataset is a collection of data. I have conceptualized it as
> > >
> > > follows: a dataset is something that can be selected, and then it is
> > >
> > > processed in a protocol-dependent way. A collection is a
> > > protocol-independent mechanism for grouping datasets.
> > I think this is what is getting us into trouble.    The concept of a
> > dataset should be independent of the services available for it:  a
> > dataset served from two different servers could very well have
> > different services/protocols available, depending on the server.  (the
> > aggregation server converts collections to datasets, for example).
> > Yet from the THREDDS/educational point of view, it is the same object.
>
> I agree with this as well.   I've been trying to reconcile how a catalog
> might look for a
> particular multifile 'dataset' which has both WMS and DODS access
> available for it.   For WMS (for multifile) datasets the access point
> would be at the
> collection level, while for 'non-aggregated' datasets the DODS access
> would
> be lower than the collection level, at the THREDDS dataset level.   It
> seems that
> the concept of a dataset resides more at the collection level, maybe the
> service
> access binding is too tightly coupled to the dataset concept in the
> current draft.
>
> Dan
>
>
> > Benno
> >
> >
> > --
> > 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)
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