xoEPC - Jan Mendling

3.4. EPC Semantics 71
have a wait context. Rules (a) and (b) indicate that if an input arc of a function or an event
is dead, then also the output arc has to have a dead context status. Rule (c) represents
that each split-connector propagates a dead context to its output arcs. These transition
relations formalize the observation that if an input arc cannot receive a token anymore,
this also holds true for its output arcs (unless they already hold positive or negative to-
kens). The join-connectors require only one dead context status at their input arcs for
reproducing it at their output arc, see (d). It is important to note that a dead context is
propagated until there is an end arc or an arc that carries a token.
(a) d
d
(b)
w
(c) d d
w
d
d
d d
w
d
(d) d
Figure 3.12: Transition relation for dead context propagation
Phase 2: Wait Context Propagation
The transition relation for wait context propagation defines rules for deriving a wait con-
text if one or more input arcs of a node have a wait context status. Figure 3.13 gives an
illustration of the transition relation. All transitions can only be applied if the respective
output arc does not hold a positive or a negative token. Concrete tokens override context
information, i.e. an arc with a positive token will always have a wait context. Rules (a)
and (b) show that if an input arc of a function or an event has a wait context, then the out-
put arc also has to have a wait context status. Rule (c) represents that each split-connector
propagates a wait context to its output arcs. The AND-join requires all inputs to have a
d
w
w
w
d
d
d
d
d
d
d