[GRASS-dev] Re: terminology issues in grass7

[Moritz Lennert]

On 16/06/09 14:29, Markus GRASS wrote:
> Moritz Lennert wrote:
>> All features without any cat value display in all layers. As Paul
>> mentioned, you have to explicitely use the cat= parameter to only
>> display features with cat values in that layer. It is debatable
>> whether there should be a flag to indicate "only show features with
>> cat values in the chosen layer", or whether this should actually be
>> the default with a flag indicating "also show features without cat
>> values". I think the first would be more appropriate and would be a
>> more convenient way than using cat=1-9999.
> It seems that this behaviour depends on the feature types defined with
> type option. In a quick test with the spearfish dataset, boundaries
> having no cats are always displayed by default, but if I select layer=2
> type=area instead of type=point,line,boundary,centroid,area,face, I get
> only the areas with a cat value in layer 2 and no boundaries, no lines,
> nothing else is displayed, and it is not necessary to use cat=1-9999.

But how you deal with the situation I described, i.e. one boundary 
segment of the polygons has a cat value in layer 2 ? I.e.

GRASS 6.5.svn (spearfish60):~ > v.category testlayers option=report
Layer/table: 1/testlayers
type       count        min        max
point          0          0          0
line           0          0          0
boundary       0          0          0
centroid       2          1          2
area           0          0          0
all            2          1          2
Layer: 2
type       count        min        max
point          0          0          0
line           0          0          0
boundary       1          1          1
centroid       0          0          0
area           0          0          0
all            1          1          1

d.vect testlayers layer=1
d.vect testlayers layer=2 type=boundary cat=1-9999 col=red width=3

gives:
http://geog-pc40.ulb.ac.be/grass/misc/testlayers1.png

I need to declare either the boundary type (or no type at all) to see 
anything in layer 2, but then it shows all boundaries:

http://geog-pc40.ulb.ac.be/grass/misc/testlayers2.png

Moritz