MIS 160 Systems Development Life Cycle I

1
MIS 160Systems Development Life Cycle I

• Lecture 12
• Behavioral Models-
• Interaction Diagrams

2
Relationship of Use Case, Class, and Interaction
Diagrams
3
Object and Class Names
4
Purpose of Behavioral Models

• To depict the internal view of business processes
• To show the effects of varied processes on the
  system

5
Interaction Diagrams

• Interaction diagrams describe how groups of
  objects collaborate in some behavior
• Represent behavior in the system
• Shows behavior of a single use case across
  multiple objects
• Two types of interaction diagrams
• sequence diagrams
• collaboration diagrams

6
Constructing Interaction Diagrams

• 1. Construct a sequence diagram for each use
  case
• a. Determine the objects involved in the use
  case
• b. Determine the communication (messages)
  between the objects
• c. Draw the sequence diagram
• 2. Construct a collaboration diagram from each
  sequence diagram
• 3. Modify use cases and class diagram as
  necessary

7
Sequence Diagrams

• Captures the behavior of a single use case
• Show the messages that pass between objects for a
  particular use-case
• Illustrate the objects that participate in a
  use-case
• Shows the sequence of events that transpire as
  objects communicate
• Represents a specific set of messages and
  interactions between objects
• Shows precise temporal order (easy to see the
  order in which things occur)

8
Sequence Diagram Syntax
AN ACTOR AN OBJECT A LIFELINE A FOCUS OF
CONTROL A MESSAGE OBJECT DESTRUCTION
anObjectaClass
aMessage()
x
9
Symbols of a Sequence Diagram
10
Sequence Diagram Development

• 1. Identify all objects and actors involved in
  scenario
• 2. Identify each message required to carry out
  scenario
• 3. Determine whether each message is always sent
  or if only sent under certain conditions

11
Sequence Diagram Development

• 4. Sequence messages correctly and attach to
  appropriate lifelines
• 5. Add formal syntax to messages
• 6. Add response messages and communications to
  complete diagram

12
Actors and Objects

• Both are things
• External
• Actors
• Role of Customer
• Physical person
• Internal
• Objects
• Computer artifacts
• Both send and receive messages

13
Messages

• Internal events identified by the flow of objects
  within a scenario
• Requests from one actor or object to another to
  do some action
• Invokes a particular method

14
Example Message-Name Formats

• Ring Telephone
• ItemInquiry ()
• CreateOrderItem (ItemId, qty)
• FirstItem OrderNumberCreateOrder ()

15
Messages

• Simple
• transfers control from one object to another
• Synchronous
• object waits for an answer to that message before
  it proceeds with its business
• Asynchronous
• object does not wait for an answer before
  proceeding
• Recursion
• an object has an operation that invokes itself

16
Message Types
17
Lifelines

• Vertical line under object or actor to show
  passage of time
• If dashed, creation and destruction of thing is
  not important for scenario
• Activation lifelines are long narrow rectangles
  used to emphasize that an object is active only
  during part of a scenario for a sequence diagram

18
Example Sequence Diagram
19
Collaboration Diagrams

• Another way of looking at interaction
• Essentially an object diagram that shows message
  passing relationships instead of aggregation or
  generalization associations.
• Emphasize the flow of messages among objects,
  rather than timing and ordering of messages
• Good at showing how objects are statically
  connected
• Collaboration and sequence diagrams are
  semantically equivalent
• Cannot easily describe concurrent messages or
  creation/deletion of objects

20
Collaboration Diagram Syntax
AN ACTOR AN OBJECT AN ASSOCIATION A
MESSAGE
anObjectaClass
21
Symbols of a Collaboration Diagram
22
Building a Collaboration Diagram

• Determine the context of the collaboration
  diagram
• Identify the participating objects and their
  associations
• Layout objects and associations
• Add messages
• Validate the sequence diagram

23
Example Collaboration Diagram