Information Technology Reference
In-Depth Information
An activity diagram shows a business process or software process
as a flow of work through a series of actions. It includes action, control
flow, initial node, activity final node, decision node, guard, and merge
node. Moreover, it can express concurrency. It uses a fork node to
divide a single flow into concurrent ones, and uses a join node to
combine concurrent flows into a single one. In UML activity dia-
grams, an action is denoted by a rounded rectangle, and labeled with
an action name of a given service class as defined in a service
ontology. The flow of control is denoted by connectors (transitions)
between actions. A decision node represents a conditional branch in a
flow, and it has one input and two or more outputs. A merge node is
required to merge flows that are split with a decision node, and it has
two or more inputs and one output. Both decision and merge nodes are
denoted by diamonds. The initial node of an activity diagram is
denoted by a filled circle, while the final one is denoted by two
concentric circles.
A simplified UML activity diagram specifying a “treating a stroke
patient” composite service is shown in Figure 6.2. In the example,
various information acquisition services and electronic medical records
service can be executed in parallel in order to acquire physiological
signals, environmental information, subjective feelings, and medical
history information of the patient. Then they are analyzed by the
cerebral apoplexy-oriented data analysis and diagnosis service, and
the risk level is determined by the personal health risk assessment
service. According to different risk levels, different solutions are
generated. The decision node in the middle part of Figure 6.2 starts
a branch structure. Three transitions (connectors) stem from the node,
and are labeled with disjoint guards—conditions that specify whether a
particular route can be taken or not.
6.2.4 User/Domain Preferences
User preferences are a key component of Web service composition.
They are critical for the following reasons.
First, according to users' requirements, a family of solutions can be
induced by a composition method. User preferences enable a user to
specify the properties of solutions that make them more or less
desirable. The composition method can use them to generate preferred
solutions.
