Biology Reference
In-Depth Information
Fig. 8. Traps and deadlocks. Two situations are considered: either transitions
t
3
and
t
4
are operative (dashed arcs) or the
transitions
t
5
and
t
6
(dash-dotted arcs).
P
1
and
P
2
, external metabolites;
S
i
, internal metabolites.
so. A trap is a set of places that - once it is sufficiently marked - can never lose all its tokens. (It can
happen that, if only some places of the trap are marked with a number of tokens smaller than a certain
limit, the trap may lose all its tokens.) Clearly, any semi-positive
P
-invariant implies a trap because the
total number of tokens is constant and can, hence, not reach zero. Moreover, superconservative subnets
