In this paper we introduce and investigate the notion of p-connectedne
ss. As it turns out, this concepts leads naturally to a unique tree re
presentation for arbitrary graphs: the leaves of this tree are the p-c
onnected components along with weak vertices, that is, vertices of the
graph that belong to no p-connected component. We then show how to re
fine this decomposition to obtain a new decomposition that extends the
well-known modular decomposition.