[OSGeodata] Re: [Geotools-devel] On the catalog tutorial

[Stefan F. Keller]

Jody,

Could'nt follow all details of your post but you hit one of the core
problems of modeling geo-information and services, namely relationships,
especially mutual relationship between these.

> Relationship to the OGC CSW 2.0 specification: the GeoTools catalog
> strongly models the containment relationship between Service and
> GeoSpatial information. All other associations are handled "implicitly"
> when working with a reference to a geospatial resource.

To me geo-information and services have a many-to-many relationship. When
there is a containment relationship with data access services containing
geo-information (which is OK for an API) and a set of containers you
obviously can compute reverse associations to re-establish this many-to-many
relationship in a libary behind an API.

As you know, I am trying to reach consensus about a minimal information
metadata model (to all: I'm still awaiting comments or counter proposals to
http://tinyurl.com/kfkyv). So I like to give my 0.25 pennies to this open
problem:
Having the use case of minimal metadata exchange - not the API - in mind,
I'm strongly proposing a containment relationship of geo-information
containing zero to many data access services (data binding protocols).

Consider also the fact that geodata can exist without data access services
but data access services can't. In addition, I'm making a difference between
data access services (as mentioned above) and 'services on it's own' like
filter or label placement services. Here I think there is no solution out
yet because these 'services on it's own' wouldn't contain associations to
specific geodata (= data access services) but would try to describe kinds
and structures of geodata they can process.

So to me, when looking for the best approach to auto-discover and publish
geo-information, I'd like to ask the following questions:
 * What's easier for webcrawlers: find data sets (or metadata about it) or
services?
* What do data providers more likely do (if they do): register data sets or
metadata about it containing some data access services or services
(containing many views to data sets)?
* And finally: What is easier to describe in a minimal metadata model: data
sets or data access services?

-- Stefan
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