Re: When

[J-M Epitalon <Jean-Marie.Epitalon@xxxxxxxxxx>]

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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