Information Technology Reference
In-Depth Information
Figure 4.5
Transform BPEL composition to SWF-net composition.
We introduce the concept of mediation to deal with this difficult
issue. Informally, mediation (or mediator) is a piece of code that
sits between two services and closes the differences between their
interfaces. Formally, we model a mediator as a colored Petri net,
which has interfaces to the two services that need to be composed to
collaborate. All messages exchanged by the two services go through
the mediator.
Definition 4.4. (Mediation/Mediator)
Amediator
M ¼
ð
P
m
;
T
m
;
F
m
;
S
m
;
is a place-bordered colored Petri net. The polarity of the border
places can be 0,
C
m
Þ
1, or
þ
1.
Remarks:
A place-bordered Petri net is a net in which (1) every
transition has at least one input and one output places; and (2) some
places have input or output transitions but not both, which are called
border places.
Definition 4.5. (Composition viaMediator)
Given two SWF-nets N
1
,
N
2
and a mediator
M
, N
1
M
P
C2
N
2
is the composition of N
1
and N
2
P
C1
via
M
.
