Information Technology Reference
In-Depth Information
order
worksheet
generation
worksheet
order
line_ws
adsl_order
inhouse_ws
nl_order
aggregation
generalization
Figure 3.2
CPN representation of generation, aggregation, and generalization relations.
generate
worksheet
); a solid transition represents the generation/
aggregation relations (
worksheet
is the aggregation of
inhouse_ws
and
line_ws
, and
order
is the generalization of
adsl_order
and
nl_order
).
For simplicity, we omit the arc expressions that represent the token
consuming relation when a connecting transition fires. In our model,
each arc will either consume exactly one token of the input place's data
type or yield one token of the output place's data type, when a connecting
transition fires.
To address the challenge of service composition from the perspec-
tive of data, first we define the property that a composite service should
satisfy. Since a composite service is represented by a colored Petri net,
we define data coherency on the latter.
Definition 3.1. (Data Coherency)
A colored Petri net
N
is data-
coherent with respect to a given business/service portfolio, if every
transition in
N
either represents an operation in the service portfolio
and transforms an input data type intoanoutput data type or represents the
aggregation or generalization relationship among data types.
Remarks:
N
is data-coherent if every transition
t
in
N
represents a
kind of data relation as shown in Figure 3.2.
Based on the formalization of a process and data, we have the
following problem statement (Figure 3.3).
Requirement is expressed as a colored Petri net with a single
transition
t
. The data types of the input and output places of
t
are denoted
