Chapter 12 Analysis Modeling

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Chapter 12Analysis Modeling
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Analysis ModelingWhere to Begin?

• Use the statement of scope and other SRS
  documents already created to guide you to
  building an analysis model.
• The analysis model will include acquired from
• the working document
• A set of use-cases
• Other items
• the statement of scope must be parsed to
  extract data, function and behavioral domain
  information

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Statement of Scope

• a relatively brief description of the system to
  be built
• indicates data that are input and output and
  basic functionality
• indicates conditional processing (at a high
  level)
• implies certain constraints and limitations

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Identifying Object and Operations
Noun/Verb Approach

• define objects by underlining all nouns in the
  written statement of scope
• producers/consumers of data
• places where data are stored
• composite data items
• define operations by double underlining all
  active verbs
• processes relevant to the application
• data transformations
• consider other services that will be required
  by the objects

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Identifying Object and Operations
Discovery Approach

• define all potential objects by thinking about
  the system. Consider everything.
• Add attributes identifying those potential
  objects which are duplicates, attributes
  themselves, operations, services.
• Add operations again identifying those potential
  objects which are duplicates, attributes,
  operations, and services.

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Identifying Object and Operations
Data Approach

• define all data entities and consider them as the
  potential objects of the system.
• Add attributes identifying those potential
  objects which are duplicates, attributes
  themselves, operations, services and adding any
  new objects needed to support attributes.
• Add operations again identifying those potential
  objects which are duplicates, attributes,
  operations, and services and adding any new
  objects needed to support operations.

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Video Rental Example

• A video store offers rental of videos to members.
  To become a member you have to have a drivers
  license and a credit card. You may rent up to 3
  videos. Corporate keeps up with trends and
  orders the tapes for rental.
• Members check out and return videos due in one
  day. Overdue fees of 1 dollar a day is charged
  for late videos.
• Upon rental a rental slip is made for customers
  which contains name, addr, city, and iterations
  of movies with tape id, movie id, title, length,
  etc.

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Video Rental System

• Use the noun approach - Grady Booch
• Use discovery approach Linda Northrup
• Use the data approach Steven Mellor, Sally
  Schaler
• Use the responsibility driven design approach
  Rebecca Wirth Brock
• Use one of above and Analysis Patterns Approach
  Joe Yoeder

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Video Rental System

• Remember these techniques identify the domain
  (conceptual) classes, not design classes, not
  programming classes, and not implementation
  classes.

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Video Rental System noun/verb

• A video store offers rental of videos to members.
  To become a member you have to have a drivers
  license and a credit card. You may rent up to 3
  videos. Corporate keeps up with trends and
  orders the tapes for rental.
• Members check out and return videos due in one
  day. Overdue fees of 1 dollar a day is charged
  for late videos.
• Upon rental a rental slip is made for customers
  which contains name, addr, city, and iterations
  of movies with tape id, movie id, title, length,
  etc.

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Video Rental System noun/verb

• A video store offers rental of videos to members.
  To become a member you have to have a drivers
  license and a credit card. You may rent up to 3
  videos. Corporate keeps up with trends and
  orders the tapes for rental.
• Members check out and return videos due in one
  day. Overdue fees of 1 dollar a day is charged
  for late videos.
• Upon rental a rental slip is made for customers
  which contains name, addr, city, and iterations
  of movies with tape id, movie id, title, length,
  etc.

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Video Rental System noun/verb
NOUNS Store Video Member License Card Corporat
e Trends Tapes Slip Customers Name Addr City I
terations Tape Movie id Title length
VERBS Offers Becomes Rents Orders Checkout Return
Charged Made contains
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Video Rental System noun/verb
Lay the nouns out on a table, 3X5 cards, chalk
board, ppt file
NOUNS Store Video Member License Card Corpo
rate Trends Tapes Slip Name
Customers Addr Iterations Movie id
Tape Title length
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Video Rental System noun/verb
Begin adding attributes
NOUNS Store Video Member License Card
name, addr.. name,length name, addr
num, name num,name, Corporate Trends Tapes
Slip Name Customers Addr Iterations Movie
id Tape name, addr..
Id num\ Title length
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Video Rental System noun/verb
Begin clustering the potential objects -
Singletons
NOUNS Store Video Member License Card
name, addr.. name,length name, addr
num, name num,name, Corporate Trends Tapes
Slip Name Customers Addr Iterations Movie
id Tape name, addr..
Id num\ Title length
Same as store only one instance
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Video Rental System noun/verb
Begin clustering the potential objects -
attributes
NOUNS Store Video Member License Card
name, addr.. name,length name, addr
num, name num,name, Corporate Trends Tapes
Slip Name Customers Addr Iterations Movie
id Tape name, addr..
Id num\ Title length
attribute
Same as store only one instance
attribute
attribute
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Video Rental System noun/verb
Begin clustering the potential objects more
attributes
NOUNS Store Video Member License Card
name, addr.. name,length name, addr

lic num, card num Trends Tapes Slip
Customers Addr name, addr..
Iterations Movie id Tape ID
Id num\
attribute
attribute
attribute
attribute
attribute
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Video Rental System noun/verb
Begin clustering the potential objects -
duplicates / descriptors
NOUNS Store Video Member name, addr..
name,length name, addr
lic
num, card num Trends Tapes Slip Customers
name, addr.. Iterations
to member
descriptor
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Video Rental System noun/verb
Begin clustering the potential objects - I/O
NOUNS Store Video Member name, addr..
name,length name, addr
lic
num, card num Trends Tapes Slip tape
id, name, addr..
I/O
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Video Rental System noun/verb
So how did we do this clustering

1. Identified all potential domain (conceptual
   classes) using the noun approach --discovery,
   data methods, or responsibility driven also work.
2. Identified potential attributes and perhaps
   operations of the potential classes.

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Video Rental System noun/verb

• 4. Eliminated some potential classes by
  clustering
• Input/Outputs (never domain classes)
• Singletons (rarely classes)
• Potential objects that turned out to be
  attributes
• Potential objects that turned out to be behaviors
• Duplicates
• Items that only described other things ( no
  attributes or methods)
• Constructed the Class Diagram and the network
  helped to cluster even more.
• Identify MM and resolved

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Video Rental System noun/verb
Begin clustering the potential objects by their
attributes and methods
Store
Video
Trends
VERBS Offers Becomes Rents Orders Checkout Return
Charged Made contains
Tape
Member
Now lets see if we can model this. Now add
cardinality, names of relationshipsresolve MM
then add attributes and methods
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Data Modeling and Entity Relationship
(E-R)Diagramming
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Why Data Modeling?

• examines data objects independently of processing
• focuses attention on the data domain
• creates a model at the customers level of
  abstraction
• indicates how data objects relate to one another

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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)
instance
each
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

themselves data items
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Typical Objects
external entities (printer, user, sensor)
things
(e.g, reports, displays, signals)
occurrences or events (e.g., interrupt, alarm)
roles
(e.g., manager, engineer, salesperson)
(e.g., division, team)
organizational units
places
(e.g., manufacturing floor)

structures (e.g., employee record)

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Data Objects and Attributes
A data object contains a set of attributes that
act as an aspect, quality, character-istic, or
descriptor of the object
object automobile attributes make model
body type price options code
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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

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ERD Notation
One common form
(0, m)
object
object
relationship
1
2
(1, 1)
attribute
Another common form
relationship
object
object
1
2
(1, 1)
(0, m)
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Building an ERD

• Level 1model all data objects (entities) and
  their connections to one another
• Level 2model all entities and relationships
• Level 3model all entities, relationships, and
  the attributes that provide further depth

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The ERD An Example
request for service
Customer
places
(1,1)
(1,m)
(1,1)
standard task table
(1,n)
work order
generates
(1,1)
(1,1)
(1,1)
(1,w)
work tasks
selected from
consists of
(1,w)
(1,i)
materials
lists
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Creating a Flow Model
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The Flow Model
Every computer-based system is an information
transform ....
computer based system
input
output
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The Flow Model
Every computer-based system is an information
transform ....
computer based system
input
output
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Flow Modeling Notation
external entity
process
data flow
data store
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External Entity
A producer or consumer of data
Examples a person, a device, a sensor
Another example computer-based system
Data must always originate somewhere and must
always be sent to something
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Process
b
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
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Data Flow
Data flows through a system, beginning as input
and be transformed into output.
base
compute triangle area
area
height
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Data Stores
Data is often stored for later use.
sensor
sensor , type, location, age
look-up sensor data
report required
type, location, age
sensor number
sensor data
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Data Flow DiagrammingGuidelines

• icons must be labeled with meaningful names
• 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

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Constructing a DFDI

• review ERD to isolate data objects and
  grammatical parse to determine operations)
• determine external entities (producers and
  consumers of data
• create a level 0 DFD

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Level 0 DFD Example
processing request
user
requested video signal
digital video processor
monitor
video source
NTSC video signal
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Constructing a DFDII

• write a narrative describing the transform
• parse to determine next level transforms
• balance to maintain data flow continuity
• develop a level 1 DFD
• use a 15 (approx.) expansion ratio

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The Data Flow Hierarchy
a
b
P
x
y
level 0
c
p2
a
f
p1
b
p4
d
5
g
p3
e
level 1
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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)

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DFDs A Look Ahead
analysis model
Maps into
design model
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Creating a Use Case Model
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The Use Case Model
Every computer-based system is a series of
actions, subsystems that interact with outside
actors (external entities).
use case
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Use Case Notation
actor
relationship (usually trigger)
use case
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Actor
A
Examples a person, a device, a sensor
Another example computer-based system
Something must trigger the action in the use
case.
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Use Case (Process)
A process triggered by a user
Examples compute taxes, determine area, Enter
student data,
These functions must be performed.
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Connection
The actors trigger the process.
use case
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Use Case Guidelines

• use cases like processes vary in granularity.
• show a good way to begin defining system
  scenarios.
• offer an abstraction which can have a test plan
• begin the traceability of the system
• has extensions
• ltltextendsgtgt for extending the functionality of a
  use case
• ltltusesgtgt for using when one use case uses another
  use case
• ltltincludegtgt for inner use of a use case inside
  another
• ltltcallsgt for invocation of other use cases.

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Constructing a Use Case

• Review the needed processes triggered by users.
• determine the actors involved.
• create the first level of use cases
• Define any extensions.

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High Level Use Cases
System
Video Rental System
Order new videos
Use Case
Corporate
Rent video
Return video
Actor
Customer
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Constructing Use Cases

• write a narrative describing the use case
• Define the classes (if known) that participate in
  that use case
• Define the pre and post conditions of the use
  case.

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Use Case Diagrams A Look Ahead
Rent video
use case model
Maps into
Customer
sequence design model
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Behavioral Modeling and Process Specification
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Behavioral Modeling
events
behavior
Outside world
Application
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The States of a System

• statea set of observable circum-stances that
  characterizes the behavior of a system at a given
  time
• state transitionthe movement from one state to
  another
• eventan occurrence that causes the system to
  exhibit some predictable form of behavior
• actionprocess that occurs as a consequence of
  making a transition

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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 transition diagram

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State Transition DiagramNotation
state
event causing transition
action that occurs
new state
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State Transition Diagram
full and start
reading
invoke manage-copying
operator
commands
full
invoke read-op-input
copies done
invoke read-op-input
making copies
reloading paper
empty
invoke reload paper
jammed
invoke problem-diagnosis
not jammed
invoke read-op-input
problem state
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Writing the Software Specification
Everyone knew exactly
what had to be done
until someone wrote it
down!