1. Static and Dynamic Modeling Using UML
REQENG

2. Requirements Engineering Activity Model
Requirements Management
Requirements Elicitation
Requirements Analysis
Requirements Specification
Requirements Validation
Validated Requirements Specification
Existing System Information
Stakeholder Needs
Organizational Standards
Technical Standards
Regulations
Domain Information
Goals

3. Requirements Analysis
The process of analyzing requirements to:
Detect and resolve requirements problems
Decompose (elaborate) requirements
Discover system boundary and how system must interact with its environment
Discover interactions and overlaps between requirements
Gain a better understanding of the problem
Includes the following main activities:
Requirements classification
Conceptual modeling
Requirements negotiation
Quality of analysis directly affects product quality
More rigorous analysis leads to better software quality

4. Subtopics Class diagram Object diagram Activity diagram
Statechart diagram

5. Class Diagram (As Part of Conceptual Modeling)
Used to create a domain model
Aids in understanding of domain and requirements
Depicts the types of objects in the problem domain
Depicts static relationships between objects
Depicts the attributes and operations of a class

6. Classes and Objects Class Object UML Notation Examples
Real world entity type about which information is stored
Represents a collection of objects with the same characteristics
Person, account, employee, car, customer
Object
Real world entity
A single “thing”
John
John’s account
An instance of a class
UML Notation
Examples

7. Attributes UML Notation Attribute Example of Attributes
Characteristic held by an object in a class
Logical data value of an object
Example of Attributes
account number, balance
Each object instance has specific value of attribute
John’s account number is 1234
Mary’s account number is 5678
Attribute name is unique within class
Example data types include Boolean, date, string, integer, real, time, and currency
Examples

8. Operations
Function or process that an object of a class knows to carry out
All objects in class have same operations
Used to query or manipulate values of attributes maintained by object
Correspond to methods
Operation is something that is invoked on an object (procedure call) while a method is the body of the procedure
UML Notation
Examples

9. Associations Static, structural relationship between classes
E.g, Employee works in Dept.
Usually read left-to-right and top-to-bottom
Inherently bi-directional
Name of association is forward direction
E.g, Employee works in Department
Opposite direction
Department has Employee
Multiplicity of Associations
Specifies how many instances of one class may relate to a single instance of another class
UML Notation
Example

10. Multiplicity of Associations
1-to-1 association
Company has President
1-to-many association
Bank manages Account
Numerically specified
Car has 2,4 Door
Optional association (0 or 1)
Customer owns Debit Card
Optional association (0, 1, or many)
Customer owns Credit Card
Many-to-Many association
Course has Student
Student attends Course

11. Association Class
Class to model association between two or more classes
Allow you to add attributes and operations to associations
Commonly used in conjunction with many-to-many associations
E.g., Many-to-many association between Project and Employee classes
Project has Employee
Employee works on project
Association Class - Hours
Attribute - Hours Worked
Not an attribute of Employee or Project
Attribute of association
UML Notation
Example

12. Generalization Relationship (Association)
IS A relationship between subclass and superclass
Subclass (child) IS A Superclass (parent)
Golfer IS AN Athlete
Captures commonalties and distinctions among like classes
Common attributes, operations, and associations captured by superclass
Subclass inherits from superclass
Distinct attributes, operations, and associations captured by subclass
Subclass is fully consistent with superclass and contains more information
Type of association
UML Notation
Example

13. Aggregation Relationship (Association)
IS PART OF Relationship
Also referred to as Whole/Part Relationship
Class B IS PART OF Class A
Class C IS PART OF Class A
Class A is composed of Class B and Class C
Arm IS PART OF human body
Leg IS PART OF human body
Human body is composed of arms, legs, ...
Used to show components of a more complex class
Distinction between composition and aggregation not real relevant to requirements
Type of association
UML Notation
Example

14. Constraint Rules
Example - a company may have only one CEO
Constraints specify conditions or restrictions that must be true
Associations, attributes, and generalization specify important constraints
UML allows other constraints to be depicted on class diagrams within “{}”
Example - an account may not have a negative balance
{balance 0}

15. Benefits of Using Class Diagrams During Requirements Analysis
Aids in understanding problem domain and domain vocabulary
Surfaces constraints
Helps to identify information requirements
Surfaces additional functional requirements

16. Guidance for Project (Static UML Model)
Include all classes and their attributes for which the requirements suggest or imply the need to remember information (Hint: may include actors from use cases)
Referred to as entity classes in project description
During requirements analysis, classes are real world entities from the problem domain, not the solution domain
Identify all associations between classes in the model
Identify any association classes
Identify cardinality of associations in model
Identify relationships among classes in the model
Generalization
Aggregation
Add applicable constraint rules
No need to identify operations
Create data dictionary to describe classes and attributes of static model

17. Subtopics Class diagram Object diagram Activity diagram
Statechart diagram

18. Object Diagram
Snapshot of objects and their relationships at a point in time
Also referred to as an instance diagram
Represents the state of the system at a point in time
Can be used to show an example configuration of objects
Contains object with values
Class diagram contains classes and attributes
Useful when the possible connections between objects are complicated
Example

19. Links Connection between object instances
UML Notation
Connection between object instances
Instance of an association between classes
E.g, Frank works on Distance Learning
Link exists between two objects if and only if there is an association between their corresponding classes
Example

20. Subtopics Class diagram Object diagram Activity diagram
Statechart diagram

21. Activity Diagram Activity diagram Activity start state activity
Describes sequence of activities with support for both conditional and parallel behavior
Variant of the state diagram in which most of the states are activity states
Activity
A state of doing something, such as typing
activity
transition
end state

22. Conditional Behavior in Activity Diagrams
Branch
Delineates conditional behavior
Single incoming transition
Several guarded outgoing transitions
Only one of the outgoing guarded transitions can be taken
Merge
Multiple incoming transitions
Single output transition
Marks end of conditional behavior started by a branch
branch
merge

23. Parallel Behavior in Activity Diagrams
Fork
Delineates parallel behavior
Single incoming transition
Several outgoing transitions
When incoming transition is triggered, all outgoing transitions are taken in parallel
Join
Multiple incoming transitions
Single output transition
Marks end of parallel behavior started by a fork
Outgoing transition is taken only when all activities with the incoming transitions have completed
fork
join

24. Example Activity Diagram

25. Other Concepts Supported by Activity Diagrams
UML Notation for Decomposition
Decomposition
Activities can be broken down into subactivities
Dynamic concurrency
Used to show iterations
Swimlanes
Conveys the people or organization responsible for carrying out each activity
Activities arranged in vertical zones separated by lines
Each zone captures responsibilities of particular organization
Denoted by multiplicity marker (*)
UML Notation for Dynamic Concurrency

26. Example Activity Diagram with Swimlanes

27. Benefits of Activity Diagrams
Useful for depicting workflow requirements
Useful for capturing required sequencing of activities
Useful for understanding business processes
Useful for describing behavior with parallel processes
Useful for analyzing a use case
Can be used in lieu of or in combination with textual use case description

28. Subtopics Class diagram Object diagram Activity diagram
Statechart diagram

29. Statechart Diagram
Describes all possible states that a particular object can get into and how object’s state changes as a result of events that reach the object
Relates events and states
Represents lifetime behavior of a single object
A particular statechart typically represents a single class

30. State Recognizable condition of an object between events
Recognizable situation during the life of an object during which it satisfies some condition, performs some activity, or waits for some event
Exists over a finite interval of time
start state
state
end state

31. State Transition
Relationship between two states that indicates when an event occurs that transitions the object from one state to another state
Represented by the line between two states
Syntax for state transition label consists of three optional parts
Event [Condition]/Action
state transition

32. Events Significant or noteworthy occurrence
A discrete signal that happens at a point in time
Has no duration
May have associated arguments
Example - telephone is taken off the hook
event

33. Conditions Boolean function Optional on statecharts
Condition is true for finite period of time
When event occurs, condition must be true for state transition to occur
If condition is false, state transition does not occur
Condition may be used to indicate that event has occurred
E.g., Closedown Requested
Can be used on statechart without a corresponding explicit event
Multiple conditions from a given state must be mutually exclusive
condition

34. State Transition Actions
Executed as a result of state transition
Executes instantaneously at state transition
Terminates itself
Is optional
action

35. Activities Activity or processing that executes for duration of state
Activity begins on entry to state
Activity ends on exit from state
Examples of activities from Gomaa cruise control example
Increase Speed
Executes for duration of Accelerating state
Maintain Speed
Executes for duration of Cruising state
Resume Cruising
Executes for duration of Resuming state
activity

36. Entry, Exit, and On Event Actions
Entry action
Action executed on entry into state
Entry / action
Exit action
Action executed on exit from state
Exit / action
On event action
Action executed while object is in a certain state and a certain event occurs that does not cause a state transition
entry action
exit action
on event action

37. Transition to Self
Transition in which the source and target states are the same
Source state is exited and reentered so exit actions and entry actions are invoked
Not equivalent to an internal transition, in which no state change occurs

38. Superstates Contains nested substates
Substate inherits the transitions of its superstate
Allows depiction of states at various levels of detail

39. Concurrent Statecharts
At any point, the object is in two states, one from the top part of the state chart and one from the bottom part of the statechart
Useful when an object has sets of independent behavior

40. When to Use Statecharts
When an object exhibits state-dependent behavior
State-independent with respect to an event
Object always responds the same way to an event
State-independent object
For all events of interest, object always reacts the same way
State-dependent object
Reacts differently to events depending on the current state
To model transactions
To describe the behavior of an object across several use cases

41. Guidelines for Project
Analyze classes from static UML model and identify those with state-dependent behavior
Develop a statechart for each object with state-dependent behavior
State names must be unique
Must be able to exit from every state
Flat statechart (no concurrency)
Object is in one state at a time
Concurrent statecharts
Object is in one state from each sub-statechart at a time
Events are considered instantaneous
Happen at a moment in time
Event name indicates something has just happened
Show start states and end states on all statecharts
Conditions must be Boolean

42. Backup Material

43. Scope Scope Lecture material on Use Case Modeling
Context diagram
Use case diagrams with accompanying textual description
Lecture material on Static and Dynamic Modeling Using UML
Class diagram
Object diagram
Activity diagram
Statechart diagram

44. UML review All problems
Given a textual description of several paragraphs, develop one or more of the artifacts on the previous slide
Given one or more artifacts, develop one or more additional artifacts
For example, given a use case with textual description, develop a statechart to depict the state-dependent behavior of a certain object
Hints
Follow UML notation very closely
Follow guidance given in lecture notes very closely
Rational Rose does not implement the full UML
If you use Rose, you may need to augment once pasted in Word or Powerpoint
Rose doesn’t do it is not a valid excuse on mid-term