1. Chapter 6-7 Analysis Modeling Adapted by Dan Fleck from: - Roger Pressman’s Slides Jochen Rick’s slides from GA Institute of Technology Extra_Examples/DFD_Example_1/ - System Analysis and Design slides edited by Yale Braunstein
Coming up: Requirements Analysis

2. Earlier Talked about requirements Frequently in written form
Supplemented by other analyses

3. Requirements Analysis
Results in models:
Scenario-based models (from POV of actors)
Data models (information domain for the problem)
Class-oriented models
Flow-oriented models
Behavioral models (how the software behaves according to external events)

4. Analysis Phase: What is it?
Software, hardware, data, human elements
Software application architecture, user interface, component-level structure
Three objectives of requirements:
To describe what the customer requires
To establish a basis for the creation of a software design
To define a set of requirements that can be validated once the software is built
Coming up: Elements of the Analysis Model

5. Elements of the Analysis Model
Scenario-based elements
Flow-oriented elements
Use-case diagrams
Use cases - text
Activity Diagrams
Swim lane diagrams
Data-flow diagrams
Control flow diagrams
Processing narratives
Analysis Model
Class-based elements
Behavioral elements
Class diagrams
Analysis Packages
CRC Models
Collaboration Diagrams
State diagrams
Sequence diagrams
ER Diagrams
Coming up: Elements of the Analysis Model

6. Typical Classes (a reminder)
External entities - printer, user, sensor
Things - reports, displays, signals
Occurrences or events (e.g., interrupt, alarm)
Roles (e.g., manager, engineer, salesperson)
Organizational units (e.g., division, team)
Places (e.g., manufacturing floor or loading dock)
Structures (e.g., sensors, four-wheeled vehicles, or computers)
But, how do we select classes?
Coming up: Selecting Classes—Criteria

7. Selecting Classes—Criteria
retained information – information about it must be remembered
needed services – operations that change the attributes
multiple attributes – if it is only one attribute, probably should be part of another class
common attributes – common things for all instances of a class
common operations – for all instances of the class
essential requirements – appear in the PROBLEM space (remember we’re doing analysis modeling!)
select a noun as a class if it fits all (or most) of these criteria (in the analysis phase)
Coming up: Selecting Classes—Example

8. Selecting Classes—Example
ATMUser
Yes
PinNum
Yes No
Maybe
retained information
needed services
multiple attributes
common attributes
common operations
essential requirements
Coming up: CRC Cards

9. CRC Cards Is there a better way to find classes?
Sure… Class Responsibility Collaborator Cards (see CRC slides and book pg 173)
Coming up: Elements of the Analysis Model

10. Elements of the Analysis Model
Scenario-based elements
Flow-oriented elements
Use-case diagrams
Use cases - text
Activity Diagrams
Swim lane diagrams
Data-flow diagrams
Control flow diagrams
Processing narratives
Analysis Model
Class-based elements
Behavioral elements
Class diagrams
Analysis Packages
CRC Models
Collaboration Diagrams
State diagrams
Sequence diagrams
ER Diagrams
Coming up: The ERD: An Example

11. The ERD: An Example request Customer for service standard work
places
request
for service
Customer
standard
task table
generates
work
order
(1,1)
selected
from
work
tasks
consists of
materials
lists
Coming up: Data Modeling

12. Data Modeling examines data objects independently of processing
focuses attention on the data domain
creates a model at the
customer’s level of abstraction
indicates how data objects relate to one another
Coming up: What is a Data Object?

13. What is a Data Object? Object —something that is described by a set
of attributes (data items) and that will be
manipulated within the software (system)
each
instance
of an object (e.g., a book)
can be identified uniquely (e.g., ISBN #)
each plays a necessary role in the system
i.e., the system could not function without
access to instances of the object
each is described by attributes that are
Data Object is similar to a class, but with no methods
themselves data items
What are some typical data objects?
Coming up: Typical Data Objects

14. Data Objects and Attributes
A data object contains a set of attributes that act as an aspect, quality, characteristic, or descriptor of the object
object: automobile
attributes:
make
model
body type
price
options code
How do data objects differ from OO classes or do they?
Coming up: What is a Relationship?

15. What is a Relationship? relationship —indicates “connectedness”;
a "fact" that must be "remembered"
by the system and cannot or is not computed
or derived mechanically
several instances of a relationship can exist
objects can be related in many different ways
Coming up: Crow’s Foot Style ERD

16. Crow’s Foot Style ERD
The ERD: Other style’s exist. There are a few, but
most are more confusing and less common than
Crow’s foot. Depending on who you ask this was
invented by Dr. Gordon Everest or Clive
Finkelstein.
Teacher teaches 0 to many classes
Classes have 1 and only 1 teacher
Students have 1 to many addresses
An address is for zero to one student (addresses may not be associated with multiple students)
Teacher
Class
Student
Address
First “thing” denotes optional or mandatory.
Second “thing” denotes cardinality (one or many)
Coming up: ERD Example: From

17. ERD Example: From http://www.b2ttraining.com
Coming up: Elements of the Analysis Model

18. Elements of the Analysis Model
Scenario-based elements
Onward to data flow diagrams!
Flow-oriented elements
Use-case diagrams
Use cases - text
Activity Diagrams
Swim lane diagrams
Data-flow diagrams
Control flow diagrams
Processing narratives
Analysis Model
Class-based elements
Behavioral elements
Class diagrams
Analysis Packages
CRC Models
Collaboration Diagrams
State diagrams
Sequence diagrams
Coming up: Flow-Oriented Modeling

19. Flow-Oriented Modeling
Represents how data objects are transformed at they move through the system
A data flow diagram (DFD) is the diagrammatic form that is used to show how data is transformed as it moves through the system
Considered by many to be an ‘old school’ approach, flow-oriented modeling continues to provide a view of the system that is unique—it should be used to supplement other analysis model elements
Coming up: The Flow Model

20. The Flow Model Every computer-based system is an
information transform ....
computer
based
system
data input
output
Coming up: Flow Modeling Notation

21. Flow Modeling Notation
external entity
process
data flow
data store
Coming up: External Entity

22. External Entity A producer or consumer of data
Examples: a person, a device, a sensor
Data must always originate somewhere
and must always be sent to something
Coming up: Process

23. Process A data transformer (changes input to output)
Examples: compute taxes, determine area,
format report, display graph
Data must always be processed in some
way to achieve system function
Coming up: Data Flow

24. Key thought: In a DFD the DATA is what is moving on the arrows!
Data Flow
Data flows through a system, beginning
as input and be transformed into output.
base
compute
triangle
area
area
height
Key thought: In a DFD the DATA is what is moving on the arrows!
Coming up: Data Stores

25. Data Stores Data is often stored for later use. look-up sensor data
sensor #, type,
location, age
look-up
sensor
data
report required
type,
location, age
sensor number
Got here 10/1/2009 (early class)
sensor data
In a real system what things are “Data Stores”?
Coming up: Data Flow Diagramming: Guidelines

26. Data Flow Diagramming: Guidelines
all icons must be labeled with
meaningful names
the DFD evolves through a number of levels of detail
always begin with a context level diagram (also called level 0)
always show external entities at level 0
always label data flow arrows
do not represent procedural logic
ensure that you show DATA moving through the system (not control)
Coming up: Constructing a DFD—I

27. Constructing a DFD—I
review the data model to isolate data objects and use a grammatical parse to determine “operations”
determine external entities (producers and consumers of data)
create a level 0 DFD
Coming up: Level 0 DFD Examples

28. Level 0 DFD Examples user digital video processor monitor video source
processing
request
user
requested
video
signal
digital
video
processor
monitor
video
source
NTSC
video signal
Coming up: Constructing a DFD—II

29. Constructing a DFD—II write a narrative describing the transform
parse to determine next level transforms
“balance” the flow to maintain data flow continuity
develop a level 1 DFD
use a 1:5 (approx.) expansion ratio
Coming up: The Data Flow Hierarchy

30. The Data Flow Hierarchyb x P y
level 0 c a p2 f p1 b p4 d 5 g p3 e
level 1
Coming up: Example DFD: Level 1

31. Example DFD: Level 1 Got here 10/1/2009 (late class)
Coming up: DFD: A practical example

32. DFD: A practical example
Launched Dec. 11, 1998, the Climate Orbiter plunged too steeply into the Martian atmosphere Sept. 23, 1999, and either burned up or crashed. In an initial failure report released Oct. 15, 2000 the review board blamed the navigation error on a communications foul-up between NASA's Jet Propulsion Laboratory and prime contractor Lockheed Martin.
Coming up: DFD Example

33. DFD Example Example from http://ldtconsultinginc.com/
Can we add labels to unlabled data flows?
Is this a level 0 diagram?
Coming up: Lets Try It

34. Lets Try It Lets create a DFD for A carpet cleaning business
A web-based order processing
system for a computer store
An address book for an iPhone
Coming up: Flow Modeling Notes

35. Flow Modeling Notes
each bubble is refined until it does just one thing
the expansion ratio decreases as the number of levels increase
most systems require between 3 and 7 levels for an adequate flow model
a single data flow item (arrow) may be expanded as levels increase (data dictionary provides information)
The things that move on the arrows
are DATA!
Got here 10/16/2008
Coming up: Elements of the Analysis Model

36. Elements of the Analysis Model
Scenario-based elements
Flow-oriented elements
Use-case diagrams
Use cases - text
Activity Diagrams
Swim lane diagrams
Data-flow diagrams
Control flow diagrams
Processing narratives
Analysis Model
Oh behave!
Class-based elements
Behavioral elements
Class diagrams
Analysis Packages
CRC Models
Collaboration Diagrams
End of Midterm Material Spring 2009
State diagrams
Sequence diagrams
Coming up: Behavioral Modeling

37. Behavioral Modeling The behavioral model indicates how
software will respond to external events
or stimuli. To create the model, the analyst must perform the following steps:
Evaluate all use-cases to fully understand the sequence of interaction within the system.
Identify events that drive the interaction sequence and understand how these events relate to specific objects.
Create a sequence diagram for each use-case.
Build a state diagram for the system.
Review the behavioral model to verify accuracy and consistency.
Coming up: State Representations

38. State Representations
In the context of behavioral modeling, two different characterizations of states must be considered:
the state of each class as the system performs its function and
the state of the system as observed from the outside as the system performs its function
What are some states for an ATM machine? Washing machine? Cell phone?
Coming up: State Diagram for the ControlPanel Class

39. State Diagram for the ControlPanel Class
Coming up: State Diagram Details

40. State Diagram Details State Name (verb in current tense)
(Optional) actions happening during state
[age <= 20]
[age > 20]
[age <= 20]/setFlag(false)
Guards: Use to describe event that causes a state transition happens (ALL transitions should have guards)
Name Examples:
sorting
validating
updating status …
Action: If something happens while transitioning to another state. (Optional)
Coming up: The States of a System

41. The States of a System
state—a set of observable circumstances that characterizes the behavior of a system at a given time
state transition —the movement from one state to another
event —an occurrence that causes the system to exhibit some predictable form of behavior
action —process that occurs as a consequence of making a transition
Coming up: Behavioral Modeling

42. Behavioral Modeling
make a list of the different states of a system (How does the system behave?)
indicate how the system makes a transition from one state to another (How does the system change state?)
indicate event
indicate action
draw a state diagram or a sequence diagram
Coming up: State Diagram - Lets Try It!

43. State Diagram - Lets Try It!
You are designing a traffic light system for this intersection.
Draw a state diagram showing the different states and how they transition.
North
West
Got here on class 2/23/2010
East
South
Coming up: Elements of the Analysis Model

44. Elements of the Analysis Model
Scenario-based elements
Flow-oriented elements
Use-case diagrams
Use cases - text
Activity Diagrams
Swim lane diagrams
Data-flow diagrams
Control flow diagrams
Processing narratives
Analysis Model
Class-based elements
Behavioral elements
Class diagrams
Analysis Packages
CRC Models
Collaboration Diagrams
State diagrams
Sequence diagrams
Coming up: Object Oriented Analysis (OOA)

45. Object Oriented Analysis (OOA)
The intent of OOA is to define all classes (and the relationships and behavior associated with them) that are relevant to the problem to be solved. For that, a number of tasks must occur:
Classes must be identified (i.e., attributes and methods)
A class hierarchy is defined
Object-to-object relationships should be
represented
Object behavior must be modeled
Tasks 1 through 4 are reapplied iteratively
Coming up: Object-Oriented Concepts

46. Analysis Model Rules of Thumb
The model should focus on requirements that are visible within the problem or business domain. The level of abstraction should be relatively high.
Each element of the analysis model should add to an overall understanding of software requirements and provide insight into the information domain, function and behavior of the system.
Delay consideration of infrastructure and other nonfunctional models until design
Minimize coupling throughout the system.
Be certain that the analysis model provides
value to all stakeholders.
Keep the model as simple as it can be.
Got here 10/6/2009
Coming up: Analysis Phase: What is it?

47. Writing the Software Specification
Everyone knew exactly what had to be done until someone wrote it down!
Read the last three slides on your own
Coming up: Specification Guidelines

48. Specification Guidelines
Coming up: Specification Guidelines

49. Specification Guidelines
Coming up: Specification Guidelines

50. Specification Guidelines
End of presentation