Re: documentation

Hi Bjørge,

Bjørge Solli wrote:

> I'm using thredds 3.4 on tomcat 5.0.30.
>
> My content/thredds/catalog.xml contains:
> <catalogRef xlink:title="North Atlantic Class 1 - Best estimate and bulletins"
>                  xlink:href="dodsC/mersea-ip-class1-nat.xml">
>     <documentation type="summary">
>                   DODS Data Prepared for the MERSEA IP EU Project.
>     </documentation>
>     <documentation type="simple"
>                   xlink:href="http://www.mersea.eu.org";
>                   xlink:title="MERSEA Project Web page">
>     </documentation>
> </catalogRef>
>
> Where is the documentation shown? 
>  
It really depends on what THREDDS client you are using. It sounds like 
you are viewing the catalogs in a browser in which case the TDS XML to 
HTML code can be thought of as the THREDDS client. In the TDS HTML 
catalogs, the documentation is only seen on datasets that have IDs (and 
are not catalogRefs, as those are links to the next level of catalog.

The NetCDF-java ToolsUI client displays the metadata for whatever 
dataset is currently selected.

> Wouldn't it be better to have a <metadata inherited="true">...</metadata> 
> inside <catalogRef> and let all the datasets in 
> dodsC/mersea-ip-class1-nat.xml inherit them? Another way that would work for 
> me was to have it like this:
> <dataset "container"> <!-- no ID on this -->
> <metadata inherited="true">...</metadata>
> <catalogRef ... />
> </dataset>
> And then all the datasets in the catalogRef also inherit the metadata.
>  
Unless the catalogRef and the referenced catalog are generated from 
datasetScan elements, the metadata in your top catalog will not be 
visible across the catalogRef link in the referenced catalog even if the 
metadata is declared inherited. Since each catalog can be referenced 
seperately, a catalog needs to stand alone. It can reference other 
catalogs and URLs but it can not depend on an upstream link that the 
user/client may not have followed. Here's how the spec puts it, "[t]he 
referenced catalog is not textually substituted into the containing 
catalog, but remains a self-contained object".

Of course, you can put the metadata in the referenced catalog by hand so 
that it is inherited by all the contained datasets. Or you can have the 
catalog(s) generated from datasetScan elements and all the metadata for 
the datasetScan will be automatically included in the generated catalogs.

> I use catalogRef to avoid having to process all my large datasets unless 
> specifically asked for, but they mainly have pretty much the same 
> <authority>, <dataType>, <dataFormat>, <documentation>, <creator> and 
> <publisher>.
>  
Are you using datasetScan elements for automatic catalog generation in 
your content/thredds/catalog.xml? Or only at lower levels of you catalog 
tree. Using datasetScan elements would do a lot of this for you and the 
catalogs don't get generated until requested.

We use catalogRef elements in our TDS configuration to split things 
apart that have very different metadata. And just to keep the pieces we 
need to maintain on a reasonable scale. The problem with using 
catalogRefs is that it often requires a bit of metadata duplication.

Hope this helps. Let me know if you have further questions.

Ethan

--
Ethan R. Davis                                Telephone: (303) 497-8155
Software Engineer                             Fax:       (303) 497-8690
UCAR Unidata Program Center                   E-mail:    address@hidden
P.O. Box 3000
Boulder, CO  80307-3000                       http://www.unidata.ucar.edu/
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