[OSGeodata] geodata schema

[Stefan F. Keller]

Tom Kralidis wrote Friday, August 04, 2006:
> TK2: we should start looking at the implementation barriers given the
> tools we already have for OGC:WFS and OAI.
[...]

I agree and I don't want to underestimate the fact that WFS is already
implemented in tools like GeoTools and others. But I assume that there is
some coding needed anyway and I wanted to give a try to get a really lean
and mean metadata protocol spec. So, if I would'nt have found something like
OAI-PMH I would vote directly for WFS profiled to RESTful harvesting needs.
Now it seems, that we got such a lightweight spec. from a much broader
community as well as tools (c.f. below).

> TK2: by "catalog", I'm referring to a XML-based API (in this case
> OGC:WFS) which allows for discovery of (in our case) geospatial content,
> via static resource or interactive service.

Yes, both static resources and online services should be included.

My simplified definition from information retrieval is, that there are
search services (called 'service providers' in OAI-PMH) which can be
subdivided in catalogues (= database, boolean search, SQL, no ranking) and
search engines (free text, fuzzy search, ranking). Mapdex.org and most GDI
portals are examples for a catalogue and geometa.info is an (initial)
example for a search engine.

Both, catalogues and search engines, can make use of the protocol I have in
mind. I observed also some additional demands, like direct search and bind
out of a GIS box (uDig and ArcGIS/geographynetwork). I hope that we can
achieve that directly through this OAI-PMH definition I sketched here:
http://www.geometa.info/rappiinfo/wiki/index.php/OSGeodata. If not I would
enhance the spec. after some implementation experiences.

> TK2: Can we step back a minute and clarify what exactly we are looking
> to do here?  Is the goal for OSGEO to stand up a catalog API into data
> and services?

Yes, that's what I suggested too in a former thread. See my answers above
and in the following message ("RE: [OSGeodata] discovery requirements").

> TK2: are there any examples, or implementations of what you have in mind
> (due to the fact that I am ignorant to OAI)?  At any rate, good
> discussion -- this is what the catalogue dilemma needs!

http://www.openarchives.org/ is the entry point of everything about OAI
including an OAI Repository Explorer as well as tools:
http://www.openarchives.org/tools/tools.html (sourceforge lists 27). I'm not
(yet) an OAI connoisseur but what I've seen so far looked like useable open
source tools. For example as data providers I found OAICat
http://www.oclc.org/research/software/oai/cat.htm for Java and
http://srepod.sourceforge.net/ for C and some PHP implementations. On the
other hand there I found search service providers from the same source as
OAICat, and additionalle FathomFive, a Java crawler based on Lucene which
spiders HTTP and OAI, up to DSpace, a digital library system. For Google,
Yahoo etc. coverage read this:
http://en.wikipedia.org/wiki/Deep_web#Crawling_the_deep_web.
I'd definitively suggest looking at OAICat.
-- Stefan
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