Information Technology Reference
In-Depth Information
Remarks:
1.
Internal places in P
I
represent the internal control logic, and
message places in P
M
represent the messages exchanged among
services.
2.
forms an ordinary WF-net as defined in Chapter 2.
3. The internal places are tagged with color e that stands for the
control tokens in P
I
;
ð
P
I
;
T
;
F
Þ
, which is unique.
4. The message places are tagged with the color sets that represent
message types.
ð
T
;
F
Þ
To differentiate input/output message places, we define message
polarity for message places, denoted
C
.
8
p
2
P
M
8
<
1
;
p
p
jj¼
þ
¼
1
^
1
ð
incoming message
Þ
1
;
p
¼
1
^
p
C
ðÞ¼
p
jj¼
1
ð
outgoing message
Þ
:
0
;
p
¼
p
¼
1
ð
constant data
Þ
The idea of message polarity comes from Reference [113], and it is
notated as shown in Table 4.1.
EXAMPLE 4.1.
Figure 4.3 shows the SWF-net of the eBay service illustrated in
Figure 4.2.
In this net, P
I
¼f
p
1
;
p
2
;
p
3
;
p
4
g
¼f
p
5
;
p
6
;
p
7
;
p
8
;
p
9
g:
and P
M
S ¼ff
g;
;
;
;
e
Order
UserID
SecretID
Token
Token
OrderID
UserID
g
, and the color mapping function C, that is, the
color set definition of each place in P, is as follows:
e denotes the color of all control tokens in all the places in P
I
.
Order, which denotes the set of all possible order messages, is the
;
OrderData
Table 4.1
The Polarity of Places
Massage place
Otherwise
Polarity (
C
)
0
þ
1
1
Undefined
