Re: Proposed new specification for THREDDSS Catalogs

[Roland Schweitzer <Roland.Schweitzer@xxxxxxxx>]

John,

I have a question about the THREDDS Dataset Inventory Catalog XML.  I 
don't intend this as a criticism, but rather I'm curious about the 
choices and trade-offs.  All of us that are messing around with XML are 
wrestling with similar issues.

In general, it seems that relationships between elements in the XML are 
done via attributes. For example, a <service> element is referred to in 
the document via the serviceName attribute in the <dataset> element.  
And a <dataset> element can be repeated by referencing the name of 
another <dataset> element via the alias attribute.

It seems to me that using this technique then requires that client code 
must be written to follow these connections.  By contrast, it seems that 
the XML community has attempted to create languages (like XPointer) that 
would "standardize" these sorts of references.  Admittedly, even though 
the XPointer recommendation is a year old, I have not found (m)any 
implementations in general purpose XML software.

Can you please comment on these choices and trade-offs for defining the 
internal connections between bit of XML that went into developing the 
Inventory Catalog?

Thanks,
Roland

John Caron wrote:

> A proposed new version of the THREDDS Dataset Inventory Catalog is 
> ready for your comments. Please send them to thredds@xxxxxxxxxxxxxxxx, 
> or to me.
>
> The new spec was created in collaboration with NCAR's Community Data 
> Portal group. It adds new types of information for "enhanced catalogs" 
> to facilitate interaction with search services and digital libraries.
>
> Annotated specification is at:
>
>  
> http://www.unidata.ucar.edu/projects/THREDDS/techNew/catalog/InvCatalogSpec.html 
>
>
> Tutorial (not complete) is at:
>
>  http://www.unidata.ucar.edu/projects/THREDDS/techNew/catalog/Primer.html
>
> The new spec is based on XML Schema. The schema is at
>
>  http://www.unidata.ucar.edu/schemas/thredds/InvCatalog.1.0.xsd
>
> Changes from version 0.6:
>
>  
> http://www.unidata.ucar.edu/projects/THREDDS/techNew/catalog/Changes1.0.txt 
>
>
>
> Thanks for any comments on this spec.