Some computational issues in membrane computing

Membrane computing is a branch of molecular computing that aims to develop models and paradigms that are biologically motivated. It identifies an unconventional computing model, namely a P system, from natural phenomena of cell evolutions and chemical reactions. Because of the nature of maximal parallelism inherent in the model, P systems have a great potential for implementing massively concurrent systems in an efficient way that would allow us to solve currently intractable problems (in much the same way as the promise of quantum and DNA computing) once future bio-technology (or silicon-technology) gives way to a practical bio-realization (or chip realization). Here we report on recent results that answer some interesting and fundamental open questions in the field. These concern computational issues such as determinism versus nondeterminism, membrane and alphabet-size hierarchies, and various notions of parallelism.