[GRASS-user] [GRASSLIST:1113] layers in vector datasets

[M S]

(sorry if this is a bit of a cross post,  but i put a similar question under
v.net.steiner.  since not everyone may realize its really a layer question i
figure'd id repost and ask)

can someone simplify an explanation about layers in grass vectors?
i read about them on this page.
http://www.geog.uni-hannover.de/grass/grass61/manuals/html61_user/vectorintro.html
its under the "attribute management" section.  it seems like they have more
to do with linking tables?

The reason i ask, is because i'm trying to input to the
v.net.steinerfunction without success.  the function (as i understand
it) requires inputs
of arc layer, and point layer, but all in same file.

when opening the "network" grass vector in QGIS, it reveals that there are 3
layers.  (which were built using v.patch to put them all together.)
layer 0 (arcs) = lines connecting buildings to streets
layer 1 (arcs) = streets
layer 1 (point) = buildings

because you specify the a(rc)layer and n(ode)layer, the fact that i have
arcs in two layers seems like it is causing the function to bail.

is there a way to put all the arcs on one layer? or is there something else
taht i am missing.  layers in vector data models are a foreign concept to me
coming from the a/i workstation world.

any help or clarification would be great!  thanks in advance.
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