[OSGeodata] discovery requirements (some thoughts)

[Stefan F. Keller]

I just wanted to ask if we still agree in defining an exchange model and a
protocol which of course should be in sync with the metadata model for
geodata?

BTW: A preliminary program of FOSS4GIS is out. Any news about a BOF session?

Here are some additional thoughts:
* Users need search services to discover geographic information.
* Geodata owners need a metadata management tool (which implies an internal
metadata model).
* Geodata owners and service providers need (i) a metadata exchange model,
(ii) an encoding of it, as well as (iii) a protocol for the exchange,
dissemination and sharing of metadata.
* Metadata should be strictly free (LGPL?).

A preliminary scenario:
* Users search or browse through metadata records. They use a web app. or a
search component out of a desktop GIS (remark: Users don't search services
per se).
* 'Search service providers' enable the discovery of geodata and 'filter
services', like transformation services (Note: WMS is a 'data access
service' and belongs to geodata not to filter services)
* 'Search service providers' gather (harvest) their information from
'data/filter service providers' and need a protocol to do this.
* 'Data/filter service providers' offer metadata over this protocol. They
typically also implement 'data access services' (WMS, WFS) or they offer
'filter services'.

Building blocks needed:
1. A geometadata management model (e.g. internal to telascience)
2. Tools to manage the geometadata
3. A geometadata exchange model
4. An encoding of the geometadata exchange model (probably XML)
5. Geometadata exchange protocols

What I am especially interested in is 3 to 5. For the protocols I see two
specifications, both already implemented and ready to go (given 2. and 3.
are determined!):
A. Simply publish XML files of geometadata (exchange model) on the web
(=HTTP with autodiscovery).
B. OAI-PMH which uses geometadata exchange model as its specialized metadata
model type (data providers needed to register but search services can do
better focussed crawling).

There are some exciting ideas around like embedding hints into the
geometadata exchange model or THUMP from IETF which lead to something
between A. and B.

-- Stefan
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