[NAS] Re: Development of an NAS interface in GDAL/OGR

[Frank Warmerdam]

Arnulf Christl wrote:
> Hi Matheuz, Frank,
> GDAL/OGR users and potential sponsors have collected ideas and 
> requirements towards a GDAL/OGR implementation for the German NAS 
> interface. They are able to provide funding for this development. Before 
> they can commit however, we have to produce a work plan and estimate 
> costs for implementation.
> I will put together some preliminary information here and send it to the 
> NAS mailing list and some individuals who are strategically involved 
> with NAS. You find a list of standards documents here: 
...
> What we need now is an estimate from you to evaluate implementation cost 
> of a first prototype that we can use to raise funding. We need to have 
> this estimate within the next four weeks and a working prototype (just 
> that no more!) until the end of the year. On that basis we can then 
> calculate a quality managed implementation that can be implemented in 
> the first quarter of 2008.

Arnulf,

I have reviewed the English V5.1 document available off this page:

http://www.adv-online.de/exteng/broker.jsp?uMen=01a700d3-6ed6-0bfb-8f23-50376a112976&sel_uCon=ba67086d-0d0d-6001-fde4-350376a11297&uTem=73d607d6-b048-65f1-80fa-29f08a07b51a.htm

I would appreciate a pointer to some reasonable representative sample data
as well as the NAS .xsd files if they don't come with the sample data.  It
is difficult for me to make meaningful estimates with it.

> == Requirements ==
> a) Develop an NAS interface converter software that implements 
> requirements as they come starting with a minimal set. Ideally the 
> implementation should be extensible to fulfill requirements that come in 
> at a later date without blocking issues. 
> b) Minimal starting point it to create geometries for land parcels, 
> buildings and connect both with the respective parcel numbers or street 
> addresses.
> c) Defer "officially certified" cartographic visualization for a later 
> date (if at all required) and when there is funding.

Cartographic visualization is outside the scope of OGR, though I can
endevour to carry through all presentation information.

It seems that an OGR reader for NAS should be practical.  But
there are data model issues:

  * OGR uses the original simple features geometry model.  Expressing
    some geometry types (eg. curves, polygonal surfaces) may be
    difficult

  * OGR will not carry an understanding of the relationships between
    features classes (layers), though it should have no problem
    carrying object ids, and object references as string attributes.

 From a code implementation point of view, a preliminary "proof
of concept" driver could likely be prepared fairly quickly and
inexpensively by making a specialized NAS version of the existing
GML reader.  The existing driver is designed for GML 2 and is
not "schema aware".  It basically does a lot of guessing based on
recognisable GML elements and internally derives something like a
schema.  An adapted driver would presumably come with pre-cooked
schema definitions for the NAS feature classes and then some
additional hacks to deal with some gml 3 issues.

I will prepare a quote on this proof of concept approach after
I have some sample data.

A longer term effort might include:
  * A rewritten xml schema aware GML driver.
  * support for GML 3 geometries.
  * support in OGR for carrying relationships between feature
    classes (object relationships).

By the way, Mateusz is not very available this fall (through to the end
of December), but depending on when the proof of concept work is to take
place it might well make sense to have him do it (with some consultation
from me).  I'll prepare a quote I'm comfortable producing and delivering
but we can stay flexible on who will actually do the work.

Finally, I'm coming to understand the importance of NAS in the German
geospatial marketplace and I'm keen to see practical support of the
data in a variety foss geospatial applications.

PS. I'll subscribe to the NAS list though of course I don't read or
write German.

Best regards,
-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org