Information Technology Reference
In-Depth Information
Remarks:
1. A service net
N
S
is data-coherent since transitions represent
data mediation or transformation. Any well-formed subnet of
N
S
is also data-coherent.
2. An SN after any refinement process in Figs. 3.4 to 3.6 is still
an SN.
Definition 3.4. (Conflict Place)
Given a service net
N
S
¼ð
P
;
T
;
F
Þ
with
T
¼
T
O
[
T
M
,
P
C
P
is a set of conflict places if
p
2
P
C
satisfying
that
p
p
, s.t.
t
>
1 and
9
t
2
2
T
O
.
An SN is
conflict-free
if it does not contain any conflict places,
that is,
P
C
¼
1
.
Definition3.5. (Reachability)
In aPetri net (
P
,
T
,
F
), we define relation
R
as the reachability relation between two nodes.
n
1
,
n
j
2
P
[
T
,
R
(
n
1
,
n
j
)
is true if there is a path
C
from
n
1
to
n
j
<
n
1
,
n
2
,...,
n
j
>
such that
(
n
i
,n
iþ
1
)
2
F
for 1
i
j
1, and for any two nodes
n
p
and
n
q
in
C
,
p
6¼
q
)
n
p
6¼
n
q
. By default,
R
(
n
i
,
n
i
)
¼
true,
8
n
i
2
P
[
T
.
3.3.2 Derive AWSP from Service Net
With the definitions given in Section 3.3.1, the problem raised in
Section 3.1.2 can be interpreted more formally.
Definition 3.6. (Feasible Solution)
Given a service portfolio, and ser-
vice composition requirement
I
!
O
,
N
is a feasible solution of require-
ment
I
!
O
if
1.
N
takes
i
as its only input and
o
as its only output;
2.
N
is data-coherent with respect to the given service portfolio and
3.
N
is an AWSP and is conflict-free.
Remarks:
Why are these requirements imposed on a feasible solution?
1. The solution should consume data
i
and yield data
o
, given the
requirement
I
!
O
.
