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Re: When
Adam,
there is a third solution:
LAS provides also for another way of creating virtual datasets (beside
categories)
In an XML datset description file, you can redefine for each variable
the actual filename that contains it;
See the following example:
<datasets>
<EC1_Historic_time_nc name="Simulation run 1 with green-house gas"
url="file:dummy.nc" doc="">
<variables>
<!-- Below, the attribute "url" allows for defining the actual file path
and name -->
<CORESERV name="RESERVOIR "
url="file:/home/glo_data/Discendo/Europe/1950-1999/EC1/EC1_1m_195001_199912_CORESERV.nc">
<link match="/lasdata/grids/Medias_flat_monthly_1950_1999_grid"/>
</CORESERV>
<PLDETESU name="TEMPERATURE "
url="file:/home/glo_data/Discendo/Europe/1950-1999/EC1/EC1_1m_195001_199912_PLDETESU.nc">
<link match="/lasdata/grids/Medias_flat_monthly_1950_1999_grid"/>
</PLDETESU>
Then, variables TEMPERATURE and RESERVOIR seem to be in the same dataset
(file): EC1_Historic_time_nc that appears under the name="Simulation run
1 with green-house gas"
Hope this helps
Jean-Marie
CERFACS
Toulouse, France
On Tue, 2005-03-22 at 17:10, Roland Schweitzer wrote:
> Adam,
>
> Adam Baxter wrote:
>
> > Thanks Everyone! It works great! I really appreciate all the help I've
> > been given.
> > One final question and I should be set. We're separating the control
> > files by variable for the moment, mostly due to system constraints .
> > From what I've seen with the xml, each dataset usually only has one
> > control file to point to. Is this correct?
> > The documentation has some information on creating categories - would
> > this be of any use to coalesce the variables under one category, even
> > if they're under different datasets due to having only one url per
> > dataset?
> >
> > Adam
>
> At the risk of confusing the situation, let me offer a few comments.
>
> The concept of a "dataset" is nebulous at best. (Personally, I don't
> even like the term since it's not even an English word, but that's
> another prejudice all together).
>
> It seems to me in the world of OPeNDAP a single URL is called a dataset
> regardless of what it contains (one variable or 20 variables). And if I
> understand your situation correctly, each of your OPeNDAP URL's points
> to an aggregation (accomplished via a GrADS control file). It's likely
> therefore that the process by which you created your LAS XML resulted in
> a pretty flat presentation of the underlying data. You likely have LAS
> XML that looks like:
>
> <datasets>
> <ds1 name="physical parameter1" url="http://gds.gov/urlpp1">
> <variables>
> <pp1 name="physical parameter 1">
> <link match="/lasdata/grids/grid1">
> </pp1>
> </variables>
> </ds1>
> </datasets>
> <datasets>
> <ds2 name="physical parameter2" url="http://gds.gov/urlpp2">
> <variables>
> <pp2 name="physical parameter 2">
> <link match="/lasdata/grids/grid1">
> </pp2>
> </variables>
> </ds2>
> </datasets>
>
> In LAS, the term dataset is used to describe a container that has
> "variables" as children. A "category" on the other hand is a container
> that has categories or datasets as children. What this means in
> practical terms, is that when you click on a dataset you get a list of
> variables each having a "check box" when allows you to select one or
> more to use. Datasets and categories appears as "links" (not check box
> items) and when you click on one you get more links (in the case of
> categories) or a list of variables with check-boxes (in the case of a
> dataset).
>
> Without using <las_categories> your presentation will always be a two
> layer hierarchy. You'll see a page of links and when you click on the
> link and you see a list of variables, but in your case it's likely that
> you list of variables each only contains 1 item (if your XML looks like
> the above).
>
> If I were faced with this situation, the first thing I would do is
> reorganize my XML to look like this:
>
> <datasets>
> <ds1 name="some interesting data" >
> <variables>
> <pp1 name="physical parameter 1" url="http://gds.gov/urlpp1">
> <link match="/lasdata/grids/grid1">
> </pp1>
> <pp2 name="physical parameter 2" url="http://gds.gov/urlpp2">
> <link match="/lasdata/grids/grid1">
> </pp2>
> </variables>
> </ds1>
> </datasets>
>
> Where related variables are grouped together (each with their own data
> url) instead of each being in a separate dataset with the url on the
> dataset element. Since you have a large collection you might want to
> invest the time to write a script that can do this manipulation for you.
>
> Then if you're satisfied with the two level presentation of the data
> that results, you're done.
>
> If you want to further group data into categories to separate say the
> "surface" data form the "upper atmosphere" data then you can start
> introducing categories.
>
> I hope this helps.
>
> Roland
>
>
>
>
>
>
>
>
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