[GRASS5] Re: Vector format proposal

[Andrea Aime]

Well, I can't say that I fully agree with you, Radim and David,
because I like a more simple approach, like teachers :-)
Anyway, freedom of choice is important and your points are
relevant, althoght in my applications they're not (I'm using
GRASS as a backend for analysis and let the user view and
manipulate data thru commercial applications, and I need vector
capabilities because I would like to perform all calculation on
server side, now vector overlays are performed client side
by Autocad Map :-( ...)
So, if I want to stick to my poor's man data representation 
(the shapefile model) I should follow some convention, 
such as putting only one type
of data in each vector map and using the following string to
associate geometry to attributes:

* 1 $MAP id $GISDBASE/$LOCATION/$MAPSET/dbf dbf

If I undestand correctly this means that every map is linked
to its own db file, that this file is named as the map and the
link it done thru an integer index. That's good for me.
If I link data thru an hypotetical PosgreSQL driver 
the thing would look something like:

* 1 $MAPSET_$MAP id geodb_$LOCATION pgsql

so that a map named geology in mapset Andrea in location Modena
would be stored in the database geodb_Modena, in a table named
Andrea_geology... will it be possible?

And what about table creation? It shold be made by hand or there
are some tools that let you specify the table structure?
And what happens when I perform a g.remove? There should be an
option to delete the table along with the data (an option, so that
I can decide to leave the table in place, too)

Let's consider a particular case of overlay: it starts from
two polygon layers and ends into a new polygon layer representing
intersection. Each polygon in the result should have attributes
from both maps (so, it is a spatial join), and I expect the result
to be linked to a new table that has columns from both of the
input tables... but what happens if the input data is linked to more
than one table? Should I cross every table with each other? Don't do
it at all and have the resulting data linked to each of the input
tables (sigh, this would be that I would have to do some kind of 
post-processing to return back to the shapefile model...)
Any idea?
Regards
Andrea Aime

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