Information Technology Reference
In-Depth Information
higher priority in user preferences. One output of the decision node points
to action
n
0
A
, the corresponding action of service
w
00
with lower priority,
and a guard is set for this control flow with the condition “Fail”. Thus,
service
w
00
can execute only after
w
0
fails. Then, we introduce a merge
node into the diagram in order to merge these two branches. Finally, we
add
n
M
into
NS
to complete the connection with SCP.
Second, for types of
WS
1
WS
n
, PPP can be
called repeatedly to deal with it. For example, if a user's preference
is of
WS
2
the form
WS
1
WS
2
WS
3
,
it can be represented as
, in which
WS
0
2
¼ð
WS
1
ð
can be viewed
as a whole. Thus, a conditional branch structure can be introduced by
executing the subprocedure once, and a fictional service
WS
0
2
is used in
the Else branch. The subprocedure is then executed to refine
WS
0
2
;a
nested If-Then-Else structure can result.
WS
2
WS
3
Þ
WS
2
WS
3
Þ
6.3.3 Illustrating Examples
Consider an online drug purchase example. It involves a series of core
tasks: searching drugs, submitting an order, paying for the order, and
finally shipping the drugs. Note that we abstract and simplify several
existing scenarios to form this example to illustrate the proposed
algorithms.
Available services and user request are listed in Table 6.1. For the
sake of simplicity, only the inputs and outputs of every service
are given. The QoS information is omitted, and this will not affect
the illustration of our method.
There are six available services, each of which accepts certain
inputs and produces certain outputs. They are as follows:
1. Given the drug name information (DrugName), service
Search-
Drugs
returns the code, price, and description information
(DrugCode, DrugPrice, DrugDescription) of the drug.
2. Given the information of drug code (DrugCode) and purchase
amount (DrugQuantity), service
SubmitOrder
returns order
information (OrderInformation) and the amount required to
pay (Payment).
3. Given the information of account number (AccountNumber)
and password (AccountPassword), service
AccountQuery
returns the account balance (AccountBalance).
