Membrane computing

As per Gheorghe Păun, the separation is of the Euclidean space into a finite “inside” and an infinite “outside”.

For example, a rule may produce the special symbol δ, in which case the membrane that contains it is dissolved and all its contents move up in the region hierarchy.

The variety of suggestions from biology and the range of possibilities to define the architecture and the functioning of a membrane-based multiset processing device are practically endless.

If objects are symbols, then their multiplicity within a region matters; however multi-sets are also used in some string models.

Particular goals can be defined to signify a halting state, at which point the result of the computation would be the objects contained in a particular region.

The P systems may trade space and time complexities and less often use models to explain natural processes in living cells.