[GRASS5] Multiple attribute support in GRASS 5.1: some considerations (long)

[Frank Warmerdam]

Andrea, etc,

I think your email on GRASS 5.1 attribute support is excellent.  A few points
from my own thoughts:

 o My thoughts on OSVecDB remain focused on what OGC calls simple
   features.  In particular, this is a non-topological approach, and it
   seems that the GRASS community does not wish to alter the approach to
   vectors this dramatically.  Thus, I think OSVecDB will not be the core
   methodology for storing GRASS vector data unless it is extended to 
   support topology. 

 o There are some very liteweight approaches to providing SQL support.  If
   you think it would be desirable for even a "base" GRASS system to have
   SQL support this might be accomplished by using something like SQLite
   which provides a high degree of SQL support bug storing data in GDBM 
   files.  Folks willing to install a real database could replace SQLite
   with PostgreSQL or something similar.  

   SQLite is at http://www.hwaci.com/sw/sqlite/ and I have been quite 
   impressed with it from my modest involvement. 

 o DBase files would be sufficient if you aren't concerned about having
   SQL support as a core service.  However, in this case I would look 
   around for a better DBF library that includes support for attributes.
   My DBF support in Shapelib is just adequate for it's purposes.  

Roger also writes that that he feels that presentation information should
be stored in close association with vectors, like the attributes.  I agree
to some extent, but I think caution should be employed.  Presentation is 
something that can grow arbitrarily complicated and this contributes 
substantially to the complexity and interchange difficulties of CAD formats
like DXF and DGN.  

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    | Geospatial Programmer for Rent

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