Tracing Some Open Problems in Membrane Computing

Membrane computing is a branch of natural computing aiming to abstract computing models from the structure and functioning of the living cell, and from the way cells cooperate in tissues, organs, or other populations of cells. This research area developed very fast, both at the theoretical level and in what concerns the applications. During the almost ten years since membrane computing was initiated, several open problems were circulated, sometimes in comprehensive lists prepared for meetings in this area. The present notes intend to survey the research related to some of these problems, mentioning both progresses made in solving them and questions which still wait for research efforts.