1. Chapter 12 Analysis Modeling

2. Analysis Modeling Two primary methods today
Structured Analysis
Object-oriented analysis
Some important considerations
Analysis products must be maintainable
Effective partitioning is essential
Graphics should be used whenever possible
Distinguish between logical and implementation

3. Elements of the Analysis Model
Primary Objectives
Describe what customer requires
Establish basis for creating software design
Define requirements that can be validated

4. Refactoring
Fowler [FOW99] defines refactoring in the following manner:
"Refactoring is the process of changing a software system in such a way that it does not alter the external behavior of the code [design] yet improves its internal structure.”
When software is refactored, the existing design is examined for
redundancy
unused design elements
inefficient or unnecessary algorithms
poorly constructed or inappropriate data structures
or any other design failure that can be corrected to yield a better design.

5. Relation of Analysis to Design

6. The structure of analysis model
Data
Dictionary
Entity
Relationship
Diagram
Data Flow
State Transition
Object
Description
Process
Specification
Control
( ERD)
(DFD)
(STD)

7. The Flow Model Every computer-based system is an
information transform ....
computer
based
system
input
output

8. Data Modeling The model consists of Data objects Data object [types]
Attributes
Relationships
Data objects
A representation of almost any composite information that must be understood by software.

9. …Data Modeling Attributes
Attributes define the properties of a data object and take on one of three different characteristics:
Name an instance of the data object
Describe the instance
Make reference to another instance
Make Model ID# Body type Color Owner
Ford Taurus Q12A Sedan Blue ABC
Lexus LS AB Sports White XYZ
Naming attributes
Descriptive
attributes
Referential
Identifier

10. …Data Modeling Relationships Defined pairwise -- many varieties Book
Bookstore
orders
displays
sells
returns

11. Cardinality and Modality
How many occurrences of object X are related to how many occurrences of object Y
One-to-one (1:1)
One-to-many (1:N)
Many-to-many (M:N)
Modality
=0 => optional relationship
=1 => relationship must appear

12. Example: Modality Customer Repair action is provided with
Mandatory: in order to have
a repair action, we must have
a customer
Optional: there may be a situation
in which a repair action is not
necessary

13. Entity Relation Diagrams (ERD)
Cornerstone of the data model -- includes
data objects,
attributes,
relationships, and
various type indicators
manufacturer
car
builds
ID#
model
body type
engine
transmission
. . .
Data Object Table

14. Example: Expanded ERD

15. Data Object type hierarchies

16. Associative Data Objects

17. Functional Modeling Data Dictionary Entity Relationship Diagram
Data Flow
State Transition
Object
Description
Process
Specification
Control
( DFD )

18. Data Flow Diagrams (DFD)
A graphical technique that depicts information flow and the transforms applied as data move from input to output
Not the same as flow charts. Does not show the logic of the transformations
Can be used at any level of abstraction

19. General Information Flow Model

20. Basic Notation

21. Information Flow RefinementB A F f V 2 X f A 6 z z f f 2 B Z 1 4 1 W f f 5 Y z 7 f 3 3 x X x f 1 f 2 Z 41 43 f 45 y Y f 1 f y 42 44 2

22. Real Time Extensions
Fundamental issue - The time at which results are produced is a part of the correctness of the computation.

23. Example: Time continuous data flow

24. Ward/Mellor Notation

25. Example: Data and control flows, Ward and Mellor

26. Hatley and Pirbhai Extensions
Use separate data flow diagram (DFD) and control flow diagram (CFD)
Data flow diagrams
Used to represent data and the processes that manipulate it
Control flow diagrams
Show how events flow among processes and show those external events that cause various processes to be activated

27. Relationship Between Models

28. Example: Data Conditions

29. CFD for Photocopier Software
paper feed status
(jammed, empty)
alarm
start/stop
manage
status
produce
Copy
Info
copying
user
read
displays
operator
input
Problem
type
Reload
status
perform
problem
reload
diagnosis
paper
full
repro
fault

30. Behavioral Modeling Description Process Object Specification Data Flow
Dictionary
Entity
Relationship
Diagram
Data Flow
State Transition
Object
Description
Process
Specification
Control
( STD )

31. State Transition Diagrams
A State is any observable mode of behavior
e.g., reading commands, computing control, waiting for next time event
States represented as rectangles
Arrows represent transitions
Value above arrow identifies event causing transition
Value below arrow indicates ensuring action

32. State Transition Diagram
reading
commands
making copies
reloading
paper
diagnosing
problem
jammed
invoke perform problem-diagnosis
empty
invoke reload paper
not jammed
invoke read-op-input
full
idle
full and start
invoke manage-coping
copies done

33. Creating an ERD List entities that customer addresses
For each, determine the connections
For each connection, create one or more object-relationship pairs
For each relationship, determine cardinality and modality
Define the attributes of each entity
Formalize and review ERD
Iterate

34. Example1: Home Security System
Initial entities
Homeowner, control panel, sensors, security system and monitoring service

35. Example2: Home Security System
Relationships between sensor and security sys.
Security system monitors sensor
Security system enables/disables sensor
Security system tests sensor
Security system programs sensor

36. Creating a Data Flow Model
First create level 0 diagram
Depict software system as single bubble
Show primary inputs and outputs
Identify processes, data objects, and data stores to be expanded at next level
Label all arrows with meaningful names
Information flow continuity must be maintained
Refine only one bubble at a time

37. Example3: Home Security System

38. Refinement Analyze textual description of bubble Examples
verbs are often processes
nouns are often external entities, data or control objects or data stores
Examples
Control panel is used to program and configure the system
Upon a sensor event, the software invokes an alarm

39. Example4: Home Security System

40. Example5: Home Security System

41. Creating Control Flow Models
Strip arrows from DFD
Add event and control items. E.g., try
List all sensors read by the software
List all interrupt conditions
List all operator actuated switches
List all data conditions
Check noun-verb parse for possible CSPEC I/O
Identify states, how each is reached and transitions
Focus on possible omissions
One of the issues here is to find the controlling events.

42. Level 1 CFD for Safe-Home

43. State transition diagram for SafeHome

44. Process Specifications
Describes all flow model processes at final level of refinement
Narrative text,
Program design language description
Mathematical equations
Tables
Diagrams
Charts

45. Data Dictionary Data Dictionary Entity Relationship Diagram Data Flow
State Transition
Object
Description
Process
Specification
Control

46. Data Dictionary
Why a data dictionary? Need an organized way to represent data & control characteristics
Usual contents
Name
Alias
Where and how used
Content description (of composite items)
Supplementary information, e.g., restrictions, limitations, preset values

47. Example Name: Shuttle pose Aliases: Position-orientation vector
Where used: Display of Shuttle on map
Content: x, y, z position wrt to Earth’s Center, roll, pitch, yaw
Supplementary Info: Elevation must be above 140 nautical miles

48. Data Structure For compositional data flow and data store elements
Describe the elements of the data structure using algebraic notation =
Composed of
{ }
Repetition
( )
Optional +
and
[ / ] or

49. Data Structure Example: Student record= student ID +
Student name+
Address +
Date of birth +
Gender +
Nationality +
Telephone number +
(mobile telephone number) +
{ course record}
Course record= course name +
Course number+
Grade

50. Data Dictionary Common tools supporting DD
Preventing creation of duplicate names
Enforce naming conventions
Printing dictionary
Determine the range of impact of changes, i.e., which processes are affected
Assist configuration management

52. End