Information Technology Reference
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We are to prove that if a mediator
M
that conforms to
I exists,
Gð
N
1
;
N
2
;
I
Þ
is well-formed. As mentioned, if a mediator
M
that conforms to I exists,
Gð
N
1
P
C1
M
P
C2
N
2
Þ
is well-formed,
and since
G
R
ð
N
1
P
C1
M
P
C2
N
2
Þ
is a subgraph of
Gð
N
1
P
C1
M
P
C2
N
2
Þ
,
it is also well-formed; and ultimately,
Gð
N
1
;
N
2
;
I
Þ
is well-formed.
V
0
;
E
0
Þ
, V
0
Remarks: G
R
¼ð
V
;
E
Þ
, V
M
1
M
2
M
M
; and
G ¼ð
M
1
M
2
. M
1
, M
2
, and M
M
are markings of N
1
, N
2
, and mediator
M
,
respectively.
G
and
G
R
are equivalent, that is, there is a surjectivemapping
v
0
2
V
0
,
v
0
w
between them such that
8
v
2
V and
8
wð
v
Þ¼
if
Q
M
1
M
2
ð
v
0
.
E
0
_ wð
v
Þ¼
ð
v
1
;
v
2
Þ2
E
)ðwð
v
1
Þ; wð
v
2
ÞÞ 2
v
1
Þ¼wð
v
2
Þ
.
v
0
,
If
in
G
there
is
v
1
t
1
i
½
v
2
t
2
i
½
v
3
...
t
k
½
i
v
k
þ
1
,
then
wð
v
1
Þ¼
R
v
0
k
þ
1
. t
1
, t
2
,...,t
k
are mediation
wð
v
2
Þ¼wð
v
3
Þ¼¼wð
v
k
þ
1
Þ¼
R
.
Q
M
1
M
2
is the projection function that projects the
transitions in
G
marking at M
1
M
2
M
M
to M
1
M
2
.
4.4 MEDIATOR GENERATION APPROACH
4.4.1 Types of Mediation
Here we first introduce the classification of mediators.
1. Store/Forward Mediator. A store/forward mediator is the
simplest one. It stores the incoming message and forwards it
to the receiver when needed.
2. Transformation Mediator. A transformation mediator trans-
forms the incoming message and forwards it to the receiver
when needed.
3. Split Mediator. A split mediator replicates the source message
(or part/element of it) into multiple copies.
4. Merge Mediator. Corresponding to a split one, a merge
mediator collects the multiple source messages/parts/elements
and then combines them into one single target message.
The CPN models for these types of mediators are given in
Figure 4.10.
