Re: New attempt
----- Original Message -----
From: "Benno Blumenthal" <address@hidden>
To: "John Caron" <address@hidden>
Sent: Wednesday, June 05, 2002 1:32 PM
Subject: Re: New attempt
> John Caron wrote:
> > One thing I dont understand is what is the relationship between whats
> > contained inside the collection vs. whats in the dataset you specify
> > the access element? The user should understand them to be the same
> > in fact the writer could accidentally or on purpose make them
> It is not a dataset that I specify through the access element -- it is a
> DODS access for the collection (collections are the same as datasets -- we
> cannot even formulate a reasonable distinction). Most collections would
> have DODS access, but some do. The writer cannot make them different,
> violates the meaning of access belonging to the collection.
Sorry, I was using the word dataset rather sloppily to indicate both the
THREDDS dataset element, and the "abstract thingy referred to by a DODS
To rephrase my question:
What is the relationship between whats contained inside the THREDDS
collection element vs. what you get back from the abstract thingy?
> > I
> > presume that the ANNUAL, MONTHLY, and SEASONAL datasets are a different
> > of accessing the collection dataset? Or should they be thought of as
> > different, but related datasets?
> They are subdatasets, i.e. different ways of accessing the collection
It sounds like they are different datasets (abstract thingy), in the sense
that you would get different data then you would from the original
> In practice this is important because some DODS clients can handle
> DODS datasets that contain nest variables (i.e. structures), and some DODS
> clients can only handle flat datasets, i.e. a collection of simple
> The DODS clients that can handle nesting can use the collection access
> DODS: DODS clients that cannot need to drill farther before using DODS.
Its not obvious how a DODS client would know it needs to drill down. There
is a valid DODS URL at each level.
> > In this spscific example, you also specify that the collection has a
> > of type Catalog <service serviceType="Catalog" suffix="thredds.xml"/>.
> > is the relationship between that catalog and what is contained in the
> > collection?
> a catalog with a single collection is the collection: your formulation as
> I can understand it (i.e. I see no different between catalogs that contain
> single collections and collections, which is implicit in your dropping the
> level of nesting under that circumstance). I think I should omit that
> reference (not that the client would get too confused: when it
> url it would find it the url of the document),
> e.g. the file should be
> <?xml version="1.0" encoding="UTF-8"?>
> <!DOCTYPE catalog SYSTEM
> <service ID="IngridDataset" serviceType="Compound"
> <service serviceType="DODS" suffix="dods"/>
> <service serviceType="Catalog" suffix="thredds.xml"/>
> <service ID="JustDODS" serviceType="DODS" suffix="dods"/>
> <dataset name="LEVITUS94">
> <attribute name="fullname" value="LEVITUS94"/>
> <access serviceID="JustDODS" urlPATH="SOURCES/.LEVITUS94/"/>
> <attribute name="references" value="Conkright:etal1994 Levitus:Boyer1994a
> Levitus:etal1994 Levitus:Boyer1994c"/>
> <documentation>LEVITUS94: World Ocean Atlas 1994, an atlas of objectively
> analyzed fields of major ocean parameters</documentation>
> <dataset name="ANNUAL">
> <access serviceID="IngridDataset" urlPATH="SOURCES/.LEVITUS94/.ANNUAL/"/>
> <dataset name="MONTHLY">
> <access serviceID="IngridDataset" urlPATH="SOURCES/.LEVITUS94/.MONTHLY/"/>
> <dataset name="SEASONAL">
> <access serviceID="IngridDataset"
> 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
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