[GRASS5] Layers Clarification

[Radim Blazek]

On 3/8/06, Trevor Wiens <twiens at interbaun.com> wrote:
> > Yes. One geometry object can be linked to more rows in attribute table.
> > In that case the geometry object has more categories (the same layer)
> > each pointing to one row in the attribute table. One category can only
> > link to one row, no more.  The relation geometry-table can be
> > one-to-many. The relation category-table can only be
> > on-to-one or many-to-one.
> >
> > It is probably much easier  get idea from a picture:
> >    http://mpa.itc.it/radim/g51/bridge.png
> > It covers all possible cases I think.
> >
>
> Radim and others,
>
> Thank you for taking the time to explain this. Is it possible to
> manually add more than one category to a geometry object or is this
> only done through automated means such as v.clean?

Yes, it is possible,
v.digit: Display categories -> Add new
QGIS: Edit Attributes -> New

> Thanks. Once I get this all straight in my head I will assemble this
> into a single document. Do you think my idea of having a statement on
> the vector module index page with a link to a more detailed explanation
> is a good idea or would somewhere else be more appropriate?

I think that it could be incorporated into
http://grass.itc.it/grass61/manuals/html61_user/vectorintro.html
(it is currently linked from main index) but you can create
a new document as well.

Radim

> T
> --
> Trevor Wiens
> twiens at interbaun.com
>
> The significant problems that we face cannot be solved at the same
> level of thinking we were at when we created them.
> (Albert Einstein)
>