[GRASS-user] Definition of Category for Vectors

[Markus Metz]

Pedro Roma wrote:
> Hi guys 
>
> I've been reading Neteler/Mitasova book and I have a question:
> Regarding vector data, what is a category?
A category specifies the category a vector feature belongs to, e.g. 
highway, major road, minor road for lines or land cover type for areas.

See also
http://grass.osgeo.org/grass64/manuals/html64_user/vectorintro.html
> and Why do I need to have category readers/writters?
In order to change categories of features.
> Because, for What I understood, a category is like a Feature ID that 
> links a geometry to its attributes in a DB. Is this correct?
Yes. Also note that one feature can have several categories and several 
features can share the same category. A link to attributes in a DB is 
optional. An example for classified (categorized) vector features 
without a db link is given in
http://grass.osgeo.org/grass64/manuals/html64_user/v.lidar.edgedetection.html

Markus M