SEKE 2012 Proceedings - Knowledge Systems Institute

Pub-T
Tc
Tc
Sub-T
Sub-T
Figure 6. The C-net description of pattern 2 based on content
Though theme can mark the exchanged parameters, its
expression to parameter is weak because theme can’t reflect the
constraint of subscription task to parameters, and its adaptation
to the change of parameter constraints is also very weak.
Meanwhile, the pub/sub model based on content allows
subscription task to express their subscription by the value of
related parameters, which has stronger ability of expression and
more flexible ability of adaptation. So we extend the workflows
by the C-net elements around publish transition, and the
additional steps are as follow:
1) Add corresponding parameter set called as
PrivateParams for each subscription transition to store all th e
parameters to be received, and add the data f low of read
operation from each subscription transition to PrivateParams;
2) Add P element to realize the delivery of the right of
occurrence from publish transition to subscription transition.
After these steps, it builds the collaboration unit of the
pub/sub model based on content, just as th e content of blue
dotted line box in figure 6, called as Content-P/S-U.
Comparing to P/S-U, Content-P/S-U has two more transitions
Tc which are mainly used to check if the parameters of
PubParams satisfy the corresponding requirements.
Sub-T Sub-T Sub-T
T
Pub-T
T
a)
b)
Figure 7. The Subject-P/S-U and Repeat-P/S-U solutions of pattern 3
Model building for pattern 3
T
T
T
Pub-T
Tm
Tm
Tm
In figure 7(a), it is a scene that a task of iterative circuit
publishes parameters which are passed to the tasks of other
parallel processes. If we use Subject-P/S-U to deal with the
data exchange as figure 7(a), there will be two problems: fist,
the publish transition will execute more than one times publish
operations. So Sub-T always can’t consume the corresponding
token in its preorder place called as Ps in time, which will be
accumulated. And there will be repeated read operations to the
same parameter set when Sub-T carries out read operation,
which decreases the efficiency of the execution of net systems.
Second, subscription transition will do more than one times
read operations. As the parameters passing way of figure 7(a),
there isn’t any method to control the read operations of Sub-T
to the following data.
Sub-T
Sub-T
Sub-T
For these two reasons, we extend Subject-P/S-U into the
collaboration unit for iterative circuit pattern, called ad Repeat-
P/S-U. The extension mainly is to add the consume mark place
Pr to indicate if Sub-T has read the parameter set and the judge
transition (called as Tm) between Ps and Sub-T to decide if
Sub-T has consume the parameters that are read, just as figure
7(b). The initial value of Pr is one token, which means the first
active read operation of Sub-T to the published data. After the
first read, the second publication of Pub-T provides Ps another
token, but the occurrence of transition Tm still need the right of
occurrence of Pr which depends on the end of all the
operations to the last set of parameters. So Tm can only inform
Sub-T the advent of new parameters after all the operations of
Sub-T, so that it prevents Sub-T to do loop detection and read
operation.
IV. CONCLUTION
In this paper, we support the model building for the data
collaboration of collaborative design based on C-net, which can
satisfy the features of process collaboration, like parallel,
iterative and dataflow oriented. We c onclude collaboration
pattern and provide a set collaboration unit model to describe
these pattern, so that all complex collaboration mechanism can
be hidden into these unite. Next step, we will prove the liveness
and safety of collaborative unit, which can validate the
rightness of data collaboration process.
ACKNOWLEDGMENT
This work was supported by the National Natural Science
Foundation of China under Granted No. 60903001
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http://ssrn.com/abstract=1886198
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