Bruce,
Given the standards based OGC CSW interface in GeoNetwork, I'd say GeoNetwork is a good backend tool for other applications to query.
One way to handle your extra metadata is to add your own metadata fields to ISO19115 by extending the base standard - you would be creating your own profile of ISO19115 - check out the schema plugins that are available for GeoNetwork for examples of how to do this - it isn't trivial but it sounds as though you need to/want to keep your metadata integrated and visible/editable by users? An advantage of doing this is that you can index and search on the additional metadata fields you add in your profile.
With your own profile in place, one way of making the XML returned by the CSW service flatter (and any XPath simpler) would be to request the results in the Dublin Core cswRecord format - you can control how and what your ISO metadata fields get mapped to in the DC cswRecord format by modifying the XSLTs that build this format from an ISO metadata record in your profile (see the present/csw subdirectory of any GeoNetwork schema to see how these work).
There are other ways that you can associate additional metadata with your ISO records in GeoNetwork (thinking about your reference to a key-value store) but most of the ones I know of work by holding an identifier (key) in the ISO record which means that you would need an extra step to extract the additional metadata (value) from wherever it is held (eg. in the openrdf repository or maybe in a related metadata record) and you would need to take care with indexing. This would make processing of CSW results a little more complex (but that might still be hidden by some coding in the CSW presentation XSLTs referred to above).
Cheers,
Simon
________________________________________
From: Bruce Crevensten [becrevensten@anonymised.com]
Sent: Tuesday, 11 September 2012 11:37 AM
To: geonetwork-users@lists.sourceforge.net
Subject: [GeoNetwork-users] Managing extra metadata through GeoNetwork, ISO 19115:2003/19139?
Hi,
I wondering if GeoNetwork is a good tool for storing arbitrary
metadata, as a backend for other apps. Our organization produces
rasters representing climate models in the Arctic, and we're currently
using GeoNetwork's ISO 19115:2003/19139 profile to store metadata
about these rasters.
We need to store additional metadata, beyond the standard ISO
templates in GeoNetwork, so that other applications can do additional
visualization, processing, and presentation.
The reason I'm exploring GeoNetwork for this is that I want to keep
the metadata about our rasters in one place (as much as possible).
Right now, we have some extra metadata hardcoded in a web app and some
other metadata in a config file, which isn't the best long-term
solution.
GeoNetwork is working fine for the core use case of storing the ISO
metadata. Where I'm running into trouble is with storing arbitrary
additional metadata (verbose and schema-oriented, where I just need a
key/value pair store) and with the querying (only getting full records
means clients are knee-deep in XPath).
I'm reluctant to build a standalone database to handle this
information because it seems like this is exactly what GeoNetwork can
(and should) do. But the friction I'm encountering when trying to use
it as a data source for other apps is making me wonder if I'm barking
up the wrong tree.
My questions are:
1. Is GeoNetwork a good tool for this use case (data source for
external applications)?
(if it is, then...)
2. Can I query GeoNetwork and get something other than the record's
XML representation? (For example, retrieve the set of extra metadata
I'm interested in as JSON)
3. What/where is the "right" place to store arbitrary additional
metadata in the ISO19115 profile? In the Ext. Info package, or...?
4. How have other folks addressed and solved this problem?
Regards,
- Bruce
--
Bruce Crevensten, Web Programmer
Scenarios Network for Alaska & Arctic Planning
www.snap.uaf.edu