I don't know your context, but maybe it will be useful to think of your structure as a semi-simplicial set http://ncatlab.org/nlab/show/semi-simplicial+set
Semi-simplicial set is a presheaf on athe semi-simplicial category, which is like the simplicial category without degeneracy maps. Every simplicial category generates a simplicial set.
Your structure forms a semi-simplicial set as it seems implicit in the question. Maybe you want the simplicial set generated by this semi-simplicial set.