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Re: latest Catalog XML

John Caron wrote:

> heres another strawman, incorporating our latest discussions:
> http://www.unidata.ucar.edu/projects/THREDDS/xml/InvCatalog.0.6d.dtd
> Recent changes:


    I've used the DTD listed above to create two examples of what
I believe I could return in an XML-based dods-dir response.  The
catalogs represent simple directory representations of dods-accessible
data; level1.xml is a higher-level directory containing only subdirs
and level2.xml is one of the subdirs containing the dods-accessible

    Both of these files validate, I get some warnings but mostly
due to style issues, there are no errors.   These examples represent
the minimum information that I could provide, there are ways I
could augment this service to provide some of the additional fields
represented in the DTD but this example is meant to illustrate a
minimum set.

    Points to note:

1: I'd need to provide 2 service elements, one for
type = DODS, and one for type = Other, where Other represents
the dods-dir service.   In many cases there will be both datafiles
and subdirectories in a file system.   Do I need to have two
service elements?   If so, in the 'Level2.xml' example how do
I indicate which service to use without adding an explicit
access element for each dataset element?

2:  I use 'collection' as a simple filesystem collection, there
may not be any meaningful relation between the files contained
in the directory other than they're accessible via the DODS DAP.

3:  Am I using 'catalogRef' correctly?  The intention is to
indicate another collection level that should only be traversed
at the user's request.


> 1) Collections as datasets. Ethan and I think the cleanest way to allow
> "collections as datasets" is to allow nested datasets. Collections remain
> just groups of datasets. A Collection as a dataset is done as a dataset with
> nested datasets. Nested dataset elements (Joe's meaning #2) should imply (in
> some way we need to clarify better) nested datasets (Joe's meaning #1 and
> #3).
> 2) allow compound services again. I have talked myself into that these will
> be often useful.
> 3) services are now contained within any collection, rather than having to
> be all in the top catalog element. They are scoped by the collection they
> are in (so we no longer use ID, since those are global). This makes a
> catalogRef have (almost) the same semantics as a collection.
> 4) a catalog now only has exactly one collection element. (i considered
> eliminating catalog but i think its better this way).
> 5) "attribute" changed to "property" (tired of saying "the attribute
> attribute")
> 6) access element can specify an absolute URL with a serverType -or- a
> reletive URL with a serverID.
> Unless I get a barrage of objections, I will document this in more detail
> ASAP. I will be gone for a week starting next Tuesdy, so Ethan will continue
> the conversation as needed. Hopefully, we can converge soon and take a
> break! I think I have incorporated all the good ideas i have heard in this
> discussion. Have I left out something, or do you think any feature is not
> worth the complexity?

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