Re: [thredds] Collection Metadata from Granules

Hi Ted,

Ted Habermann wrote:

We would be very interested in working with you to explore adding this harvesting approach to GeoNetwork. I expect that there will be a plethora of challenges. I am using this e-mail to collect and expose my, admittedly long-winded and certainly primordial, thoughts on a couple, and possibly to initiate discussion and evolution...

Content - My experience (could easily be incorrect) is that the THREDDS community has really focused on “use” metadata which tends to be relatively sparse (most importantly) and generally more customized. This reflects the emergence of THREDDS from the scientific community which traditionally shares that focus. As a result, I expect that the threddsmetadata elements exist only in a small minority of catalogs. This situation is exacerbated by the evolution of THREDDS towards auto-generation of catalogs from file systems. I’m fairly sure that this process does not involve opening the files (for performance reasons) so metadata that might be in those files is generally not incorporated in the catalog. I suspect that hand-hewn catalogs with lots of metadata are rare. BTW - I suspect that the same obvious (over-)generalization applies to the files that underlie most of these catalogs (again I have no real quantitative evidence for this). There are a few groups out there creating netCDF files with really high-quality metadata content and that number may be growing, but it is still small. This reflects the fact that most creators and users of these files understand them pretty well and can generally use them successfully with information gleaned from conversations or scientific papers and presentations. The focus on high-quality standard metadata generally comes more from archives and groups interested in the preservation of understanding. This is a different group.
Yep - I think I understand where you are coming from. The projects I'm working with (and the institution I work for) are trying to do the high-quality standard metadata approach because they've realized its importance for data management. Tools like THREDDS, GeoNetwork, other OGC servers etc are to be introduced as part of a data management policy with procedures/principles etc. This and links between the tools (such as a THREDDS metadata harvester) are intended (however optimistic that may sound!) to try and change the culture of "metadata for me and my collaborators only". From this point of view, THREDDS has a number of really useful features - eg. metadata inheritance in the catalog being one of them and the potential to use datasetScan catalogs (from filesystems or even other OPeNDAP servers) to build enhanced catalogs with metadata elements embedded is another.

I have to leave comment on the rest of your points until I've had more time to think about them (apologies) and study your slides :-)

Cheers and thanks,
Simon



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