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Talk:P systems with symport-antiport - Scholarpedia

Talk:P systems with symport-antiport

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    P systems with symport/antiport are one of the most studied models in membrane computing. Their simple and elegant way to operate has caught the interest of many researchers and several papers have been written on this model or inspired by the operations used by it.

    - several -> many

    In this article we describe the biological processes that inspired this abstract model of computation and we briefly summarise the known results. Due to the nature of Scholarpedia, what presented here is rather informal. Formal definitions and proofs can be found in the provided comprehensive bibliography.

    - currently the given bibliography is far from comprehensive. You might want to mention that the current state-of-the-art is a result of a few series of original results and improvements by A. Alhazov, I. Ardelean, F. Bernardini, M. Cavaliere, E. Csuhaj-Varju, R. Freund, P. Frisco, M. Gheorghe, H.J. Hoogeboom, O.H. Ibarra, M. Ionescu, L. Kari, S.N. Krishna, M. Margenstern, C. Martin-Vide, M. Oswald, A. Paun, Gh. Paun, J. Pazos, A. Rodriguez-Paton, M.J. Perez-Jimenez, V. Rogojin, Yu. Rogozhin, G. Rozenberg, Gy. Vaszil, S. Verlan, S. Woodworth and others.

    Theoretical devices in membrane computing, P systems with symport/antiport consist of a set of nested membranes defining compartments. The nesting present in P systems with symport/antiport is hierarchical and it defines a cell-tree: a compartment can be contained in at most one compartment and it can contain several compartments. Within each compartments there may be objects evolving and moving to neighbouring membranes following rules specified for the particular system. Outside the outer membrane, the environment is subject to its own set of rules.

    - usually in membrane computing there are no rules associated with the environment

    In P systems with symport/antiport, as introduced in Păun A., Păun Gh. (2002), computation is restricted to the synchronous movement of objects from one compartment into another. This means that the system contains unstructured objects that are not rewritten or changed in any other way. A configuration of the system is given by a finite multiset for each of the compartments; each compartment contains a finite number of objects, whereas the objects initially present in the environment are assumed to have infinite (unbounded) supply. Rules associated to the compartments and inspired by the protein mediated transport described in the previous section, are of one of the following forms, where x and y are strings of objects (representing multisets in the obvious way):

    - typically symport/antiport P systems are described in terms of rules associated to membranes, not compartments. Indeed, they govern the passage of objects through the associated membrane, whereas reasoning in terms of parent compartment, although equivalent, is far less intuitive.

    This system is consists of three compartments (plus the environment) each surrounded by a membrane numbered 1, 2 or 3..

    - is consists -> consists

    In the previous section we said that the result of a computation is the number of objects present in a designed membrane called output membrane and that this output membrane has to be elementary. As the only elementary membrane in the system in Figure 2 is membrane 3, and as in this system the compartment defined by this membrane can only collect an even number of A's, then we can say that this system computes even numbers.

    - computes -> generates

    Researchers in P systems with symport/antiport were interested to answer, in between others, the following questions:

    - in between -> besides

    Also here, for the sake of brevity, we do not mention the number of symbols left in the output compartments in each computation. Readers interested in these details can refer to the given references on P systems

    - "we do not mention the number of symbols left in the output compartments": this is nonsense, since precisely this is the result. You probably mean the number of additional symbols, but then you CANNOT use the formal notation unless you modify the definitions accordingly.

    degree max. weight symport max. weight antiport class of numbers 1 1 1 \subseteq NFIN 1 2 0 \subseteq NFIN 1 1 2 = NRE 1 0 2 = NRE 1 3 0 = NRE 2 1 1 = NRE 2 2 0 = NRE

    - the last 4 lines are formally not correct

    Cells can be connected to each other so to form tissues. Our skin, guts and muscles are examples of tissues.

    - so to form -> to form

    Păun, Gh.; Rozenberg, G. and Salomaa, A. (2010). The Oxford Handbook of Membrane Computing. Oxford University Press, Oxford.

    - Please mention that you refer to Chapter 5 (R. Freund, A. Alhazov, Yu. Rogozhin, S. Verlan: Communication P Systems. 118-143.)

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