121
(S(e
1
), S(e
2
)) = I(S(e
1
), S(e
2
))
to indicate the fact that the transition is determined solely by
the state of the entities, or in other words, that the fate of a
cell depends upon what it actually is (i.e., the activation state
or maturation stage). Mathematicians would call this cellular
dynamics a Markov process.
3.2.1 Entity-state Description
The model entities are either cells or molecules. From the point
of view of a computer programmer, the former need to be
represented by a much more sophisticated data structure because
of their inherent higher complexity. In particular, cells have an
internal dynamics, which translates as a variable to store the
internal state, one for each instance. Moreover, each lymphocyte
is equipped with a receptor ...