SEKE 2012 Proceedings - Knowledge Systems Institute

optimization which can improve multidisciplinary design. The
specific abstract process of pattern 2 is as figure 2:
r1 r2 r3
T2
T1
T3
superior process and subordinate process and will cause the net
system too complex to implement and analyze. So we use an
unified middle data set variable to stand for the summarized
parameters, and add the corresponding P-occurrence
mechanism, which is called as DX-U, just the abbreviation of
the collaboration unite of unidirectional summarization of data,
just as figure 4.
k1 k2 k4
T4
T5
T
k3
T6
d[0]
d[1]
d[l]
Figure 2.
Task interaction pattern between parallel processes
T2
Ti
In figure 2, transition T3 separately reads parameters sets of
r1 and k3, and transition r2 and k2 also read parameters set
produced by T2. They together produce complex parameter
passing route, but these scattered data flows can’t reflect the
synchronous relationship between the transition which executes
write operation and the transition which executes read
operation. At the same time, the parameters sets of these
parameter passing flows always cause the redundancy of data
transition because of the common design contents.
Pattern 3 : task interaction between iterative processes
This pattern is reflected into the scene that one or more
transitions of iterative circuit pass parameters to the transitions
of other parallel design processes. This pattern mainly
describes the complex data exchange problem which is caused
by multi-version process parameters produced by the iterative
execution of Repeat. The multi-version property of Repeat will
affect the parallel execution of other processes which exchange
parameters with Repeat, and the specific abstract process of
pattern 2 is as figure 3:
T3
Tj
Figure 4. The C-net description of task interaction pattern between superior
process and subordinate process
In DX-U, it uses the unified set d of parameter variables to
collect the parameter set of the related tasks, just as follow:
d T2. params Ti. params Tj.
params
Model building for pattern 2
The pub/sub model can be used to extend unidirectional
data passing to describe complex parameter exchange between
transitions effectively, and the ability of expression for
parameter subscription directly affects flexibility of data
collaboration between transitions. Now there are mainly two
kinds of pub/sub model: the model based on theme and t he
model based on content. For parameter passing of the pub/sub
model based on theme, the expression by C-net is as follow:
r1 r2 r3
T1
Ti
Tr
k1 k2 k4
k3
Tj
T2
T4
T1
T6
T3
T5
r1 r2 r3
Figure 3. Task interaction pattern between iterative processes
Figure 3 describes a scene that a task Tr of iterative process
Repeat(i,j) publishes parameters to the tasks of other parallel
processes, including a2, r2 and t4. The difference between
pattern 2 and 3 is that the parameter passing will execute more
than one times and produce the process data of different
versions, which makes collaboration process more complex.
C. Process collaboration based on C-net
According to the features of these process collaboration
patterns, we provide their model building based on C-net.
Model building for pattern 1
In pattern 1, if we set V element for each parameter passing
flow to stand for corresponding parameter set, it can’t unified
the interaction in the form of parameter collection between
Sub-T Sub-T Sub-T
Pub-T
k1 k2 k4
T6
Figure 5. The C-net description of pattern 2 based on theme
k3
P/S-U
T2
T4
T3
T5
Considering the feature of task interaction of parallel
processes, we extend the process collaboration based on
publish transition centered, and the operations include:
1) Set corresponding published parameter set called
PubParams for each transition that executes read operation, so
that let PubParams store the parameter set transited at runtime;
2) Add the data flow of write operation and read operation
of PubParams;
3) Add P element to realize th e occurrence right of
parameter passing process f rom publish transition to
subscription transition, which will build a P-occurrence unit of
pub/sub model based on th eme, as the content of dotted line
box in figure 5(a), called as P/S-U. According the above steps,
we take the publish transition T4 for example, in which the
token of Pub-t in P/S-U comes from T4, just as figure 5(b), and
we can deal with r1 and k3 in figure 5 by the same way.
543