Quote - Say a model has 10 verices witch is refered to from 0 to 9 in the face data.
Say that the vertices from 3 to 6 belongs to group A and the rest to group B.
Now if I want to export the verticese for group B they should be
0-2 followed by 7-9(jumping over the vertices belonging to groupA).

As far as I remeber thats also the only data that is needed for a morph.

Is this correct?

Yes. Actually vertices are numbered starting from 1, but you have the general idea right. You can use an OBJ file containing only vertices as a morph target, but most modellers will want facet definitions before you'll be able to see the mesh and edit it.