Reading Techniques for OO Design Inspections

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Reading Techniques for OO Design Inspections
Jeff Carver Forrest Shull Guilherme H.
Travassos Victor R. Basili basili,
carver_at_cs.umd.edu fshull_at_fraunhofer.org http//w
ww.cs.umd.edu/projects/SoftEng/ESEG/

• UFRJ
• COPPE

Department of Computer Science Experimental
Software Engineering Group
Fraunhofer Center - Maryland
2
Reading Techniques for OO Design

• OORTs (Object Oriented Reading Techniques)
• A family of reading techniques that can be used
  to read OO design artifacts against
• 1. themselves, and
• 2. requirements descriptions and use-cases
• within a domain in order to identify defects
  among them.
• Its a defect based family reading approach

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Reading Techniques for OO Design
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Reading Techniques for OO Design
Looking for discrepancies
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Reading Techniques for OO Design
Looking for discrepancies
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Reading Techniques for OO Design

• UML Artifacts

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Horizontal Reading Techniques

• Ensure all design artifacts represent the same
  system
• Design contain complementary views of the
  information
• Static (class diagrams)
• Dynamic (interaction diagrams)
• Not obvious how to compare these different
  perspectives

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Vertical Reading Techniques

• Ensure that the design artifacts represent the
  same system described by the requirements and
  use-cases
• Comparing documents from different lifecycle
  phases
• Level of abstraction and detail are different

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What we know so far

• Techniques are feasible
• Techniques help find defects
• Vertical reading finds more OMISSION and
  INCORRECT FACT discrepancies
• Horizontal reading finds more INCONSISTENCY and
  AMBIGUITY discrepancies

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Reading Techniques for OO DesignTeam
Organization
An inspection process with OO reading techniques
looking for consistency horizontal reading
Reader 1
Meet as a team to develop a comprehensive defect
list. Each reader is an expert in a different
aspect
looking for consistency horizontal reading
Reader 2
looking for traceability vertical reading
Final list of all defects sent to designer for
repairing
Reader 3
REMEMBER Finding defects not fixing defects
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Reading Techniques for OO Design

• Target Artifacts

Requirements
Requirements
Use-Cases
Specification
Descriptions
Class
Class
State Machine
Interaction
High Level
Diagrams
Descriptions
Diagrams
Diagrams
Design
(Sequence)
Vertical reading
Horizontal
reading
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Example Gas Station Control System (GSCS)

• Recall our description of the system
• ... The gas station allows customers to purchase
  gas (self-service) or to pay for maintenance work
  done on their cars. Some local businesses may
  have billing accounts set up so that the business
  is sent a monthly bill, rather than paying for
  each transaction at the time of purchase. There
  will always be a cashier on-duty at the gas
  station to accept cash payments or perform system
  maintenance, as necessary.
• The requirements in this excerpt ...concern how
  the system receives payment from the customer. A
  customer has the option to be billed
  automatically at the time of purchase, or to be
  sent a monthly bill and pay at that time.
  Customers can always pay via cash or credit card.
  

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Defining levels of Functionality

• Requirement Requirement describes the high-level
  functions of the system. Typically, requirements
  are described from the users point of view.
• Behavior Behaviors are low-level actions
  performed by the system they are the atomic
  units out of which system requirements are
  composed. Users do not typically consider
  behaviors an end in themselves rather, behaviors
  are the steps by which some larger goal or
  requirement is achieved.
• Operation Operations are the very lowest-level
  actions out of which system behaviors and, in
  turn, requirments are composed. They represent
  the communication between objects that work
  together to implement system functionality.
  Operations may be shown on sequence diagrams and
  must have associated object behaviors.

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Example Abstracting operations to behaviors (to
requirements) in GSCS
A customer, giving his account_number, asks for
an available parking spot to park his car. To
get an available parking spot gas station owner
searches for the next parking place
available. With this information the customer can
confirm the lease of the parking place. The time
of payment (time of purchase or a monthly paper
bill) and how the service should be paid (by
cash, personal check or credit card). If the
time of payment is the same as the purchase time
and Customer decides to pay by Credit Card then
Credit Card system should be used. The Customer
can only wait for 30 seconds for the
authorization process otherwise this payment
should made by cash or personal check to avoid
other Customers waiting on the lane. It allows
the Gas Station Owner to mark a new service
purchase for this Customer at this date.
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Reading Techniques Semantic Checking

• Operations Sequence diagram describes
  communications between objects.
• E.g. parking_spot_request(), next_available()

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Reading Techniques Semantic Checking

• Behavior Requirements, class methods, state
  diagrams often refer to behaviors provided by the
  system
• E.g. get an available parking spot, pay by
  credit card

Requirement Reserve a Parking spot with a Credit
Card
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Constraints/Conditions

• Condition
• Describes the situation that must be true for the
  functionality/service/message to which it is
  attached to be executed.
• Constraint
• Describes something that always has to be true in
  the system.
• Is not dependent on the functionality being
  executed.

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Reading Techniques Semantic Checking

• Requirements often describe conditions and
  constraints on functionality.
• If the time of payment is the same as the
  purchase time and Customer decides to pay by
  Credit Card then Credit Card system should be
  used. The Customer can only wait for 30 seconds
  for the authorization process otherwise this
  payment should be made by cash or personal check
  to avoid other Customers waiting on the lane. The
  Gas Station Owner should ask the Customer for a
  new payment type.

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Example Conditions and Constraints
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Example Constraints/Conditions GSCS
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Discrepancy Report Forms
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Discrepancy Report - Horizontal
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Discrepancy Report - Vertical
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Reading Techniques
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Object model and Classification Diagram x
Sequence diagrams

• The artifacts
• An object model and classification diagram that
  describe the objects of a system and how they are
  associated.
• Sequence diagrams that describe the classes,
  objects, and possibly actors of a system and how
  they collaborate to capture services of the
  system.
• The goal
• To verify that the object model and
  classification diagram for the system describes
  classes and their relationships in such a way
  that the behaviors specified in the sequence
  diagrams are correctly captured.

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Object model and Classification Diagram x
Sequence diagrams

• Step 1
• Inputs Sequence diagram.
• Outputs System objects Behaviors of the system
  Conditions on the behaviors.
• General instructions Take a sequence diagram and
  read it to understand the system behaviors
  described and how the system should implement
  those behaviors.
• Specific instructions
• Identify the system objects and classes, and any
  actors.
• Identify the information exchanged between
  objects (the horizontal arrows). If the
  information exchanged is very detailed, at the
  level of operations, you should abstract several
  operations together to understand the behaviors
  they work to provide.
• Identify any constraints on the operations and
  behaviors.

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Object model and Classification Diagram x
Sequence diagrams
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Object model and Classification Diagram x
Sequence diagrams

• Step 1
• Inputs Sequence diagram.
• Outputs System objects Behaviors of the system
  Conditions on the behaviors.
• General instructions Take a sequence diagram and
  read it to understand the system behaviors
  described and how the system should implement
  those behaviors.
• Specific instructions
• Identify the system objects and classes, and any
  actors.
• Identify the information exchanged between
  objects (the horizontal arrows). If the
  information exchanged is very detailed, at the
  level of operations, you should abstract several
  operations together to understand the behaviors
  they work to provide.
• Identify any constraints on the operations and
  behaviors.

29
Object model and Classification Diagram x
Sequence diagrams
Get an available parking spot
Pay by Credit Card
Pay by Monthly Bill
30
Object model and Classification Diagram x
Sequence diagrams

• Step 1
• Inputs Sequence diagram.
• Outputs System objects Behaviors of the system
  Conditions on the behaviors.
• General instructions Take a sequence diagram and
  read it to understand the system behaviors
  described and how the system should implement
  those behaviors.
• Specific instructions
• Identify the system objects and classes, and any
  actors.
• Identify the information exchanged between
  objects (the horizontal arrows). If the
  information exchanged is very detailed, at the
  level of operations, you should abstract several
  operations together to understand the behaviors
  they work to provide.
• Identify any constraints on the operations and
  behaviors.

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Object model and Classification Diagram x
Sequence diagrams
Get an available parking spot
Pay by Credit Card
Pay by Monthly Bill
32
Object model and Classification Diagram x
Sequence diagrams

• Step 2
• Inputs Sequence diagrams, with objects,
  behaviors, and constraints marked Object model
  and classification diagram.
• Outputs Discrepancy reports.
• General instructions Identify and inspect the
  related object model, to identify if the
  corresponding system objects are described
  accurately.
• Specific instructions
• Verify that every object, class, and actor used
  in the sequence diagram is represented by a
  concrete class in a object model.

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Object model and Classification Diagram x
Sequence diagrams
Get an available parking spot
Pay by Credit Card
Pay by Monthly Bill
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Object model and Classification Diagram x
Sequence diagrams
???
Discrepancy
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Object model and Classification Diagram x
Sequence diagrams

• Step 2 (cont.)
• Verify that for every behavior or operation on
  the sequence diagram, there is a corresponding
  operation on the object model. Verify that there
  are class behaviors in the class diagram that
  encapsulate the higher-level behaviors provided
  by the sequence diagram. Verify that for each
  behavior, the operations described by the
  sequence diagram are sufficient to achieve that
  behavior.Is there an operation on the sequence
  diagram for which the receiving object does not
  contain an appropriate behavior on the object
  model?
• Are there appropriate class behaviors for the
  system behaviors?
• Is there an association on the classification
  diagram between the two objects between which the
  operation goes?

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Object model and Classification Diagram x
Sequence diagrams
Get an available parking spot
Pay by Credit Card
Pay by Monthly Bill
37
(No Transcript)
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Object model and Classification Diagram x
Sequence diagrams
Get an available parking spot
Pay by Credit Card
Discrepancy
Pay by Monthly Bill
39
Object model and Classification Diagram x
Sequence diagrams

• Step 2 (cont.)
• Verify that the constraints identified in the
  sequence diagram can be fulfilled according to
  the object model.Is all of the information
  concerning constraints on the sequence diagram
  captured on the object model?

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Object model and Classification Diagram x
Sequence diagrams
Get an available parking spot
Pay by Credit Card
Pay by Monthly Bill
41
Object model and Classification Diagram x
Sequence diagrams
42
Object model and Classification Diagram x
Sequence diagrams

• Step 2 (cont.)
• For each class, operation, and data identified
  above, think about whether, based on your
  previous experience, it results in a reasonable
  design. Does it make sense for the class to
  receive this operation with these data? Could you
  verify if the constraints are feasible? Are all
  of the necessary attributes defined?
• For the classes specified in the sequence
  diagram, do the behaviors and attributes
  specified for them on the operations model make
  sense? Is the name of the class appropriate for
  the domain, and for its attributes and behaviors?
  Are the relationships with other classes
  appropriate? Are the relationships of the right
  type?

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Sequence diagram x Requirements and Use Cases

• The artifacts
• A requirement and associated use case(s) that
  describe important concepts of the system and the
  services it provides.
• One or more sequence diagrams that describe the
  objects of a system and the services it provides.
  
• The goal
• To verify that sequence diagrams describe an
  appropriate combination of objects and messages
  that work to capture the functionality described
  by the requirement and use case.

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Sequence diagram x Requirements and Use Cases

• Step 1
• Inputs A Requirement and associated use case.
• Outputs System concepts Behaviors provided by
  systemData necessary for achieving behaviors.
• General instructions Identify the functionality
  described by a requirement and use case, and
  important concepts of the system that are
  necessary to achieve that functionality.
• Specific instructions
• Find system concepts in the requirement and use
  case.
• For each concept, identify the behaviors in which
  it is involved. Look for associated constraints
  and conditions.
• Also identify any information or data that is
  required to be sent or received in order to
  achieve the behaviors.

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Sequence diagram x Requirements and Use Cases
Text from Requirement/Use Case
- A customer, giving his account_number, asks for
an available parking spot to park his car. - To
get an available parking spot, the gas station
owner searches for the next available parking
place. - With this information the customer can
confirm the lease of the parking place. - The
time of payment (time of purchase or a monthly
paper bill) and how the service should be paid
(by cash, personal check or credit card) should
be given. - If the time of payment is the same
as the purchase time and Customer decides to pay
by Credit Card then Credit Card system should be
used. The Customer can only wait for 30 seconds
for the authorization process otherwise this
payment should made by cash or personal check to
avoid other Customers waiting on the lane. - It
allows the Gas Station Owner to mark a new
service purchase for this Customer at this date.
46
Sequence diagram x Requirements and Use Cases

• Step 2
• Inputs Requirement, Use case, sequence diagram.
• Outputs System concepts Behaviors provided by
  systemData exchanged between objects.
• General instructions Identify and inspect the
  related sequence diagrams, to identify if the
  corresponding functionality is described
  accurately and whether behaviors and data are
  represented in the right order.
• Specific instructions
• For each sequence diagram, identify the system
  objects.
• Identify the behaviors described by the sequence
  diagrams.
• Identify the information (or data) that is
  exchanged between system objects.

47
Sequence diagram x Requirements and Use Cases
48
Sequence diagram x Requirements and Use Cases

• Step 2
• Inputs Requirement, Use case, sequence diagram.
• Outputs System concepts Behaviors provided by
  systemData exchanged between objects.
• General instructions Identify and inspect the
  related sequence diagrams, to identify if the
  corresponding functionality is described
  accurately and whether behaviors and data are
  represented in the right order.
• Specific instructions
• For each sequence diagram, identify the system
  objects.
• Identify the behaviors described by the sequence
  diagrams.
• Identify the information (or data) that is
  exchanged between system objects.

49
Sequence diagram x Requirements and Use Cases
Get an available parking spot
Pay by Credit Card
50
Sequence diagram x Requirements and Use Cases

• Step 2
• Inputs Requirement, Use case, sequence diagram.
• Outputs System concepts Behaviors provided by
  systemData exchanged between objects.
• General instructions Identify and inspect the
  related sequence diagrams, to identify if the
  corresponding functionality is described
  accurately and whether operations and data are
  represented in the right order.
• Specific instructions
• For each sequence diagram, identify the system
  objects.
• Identify the behaviors described by the sequence
  diagrams.
• Identify the information (or data) that is
  exchanged between system objects.

51
Sequence diagram x Requirements and Use Cases
Get an available parking spot
Pay by Credit Card
52
Sequence diagram x Requirements and Use Cases

• Step 3
• Inputs Requirement, Use case, sequence diagram.
• Outputs Discrepancy reports.
• General instructions Compare the marked-up
  diagrams to determine whether they represent the
  same domain concepts.
• Specific instructions
• For each of identified concepts on the
  requirement and use case, search the sequence
  diagram to see if it is represented.
• For each object on the sequence diagram search
  the requirement and use cases to see if it is
  represented.

53
Sequence diagram x Requirements and Use Cases
Text from Requirement/Use Case
- A customer, giving his account_number, asks for
an available parking spot to park his car. - To
get an available parking spot, the gas station
owner searches for the next available parking
place. - With this information the customer can
confirm the lease of the parking place. - The
time of payment (time of purchase or a monthly
paper bill) and how the service should be paid
(by cash, personal check or credit card) should
be given. - If the time of payment is the same
as the purchase time and Customer decides to pay
by Credit Card then Credit Card system should be
used. The Customer can only wait for 30 seconds
for the authorization process otherwise this
payment should made by cash or personal check to
avoid other Customers waiting on the lane. - It
allows the Gas Station Owner to mark a new
service purchase for this Customer at this date.
54
Sequence diagram x Requirements and Use Cases
Get an available parking spot
Discrepancy
Pay by Credit Card
55
Sequence diagram x Requirements and Use Cases

• Step 3 (cont.)
• Identify the behaviors described by the sequence
  diagram, and compare them with the description
  used on the requirement and use case. Do the
  objects exchange operations in the same specified
  order? Are all transported data in the right
  operations? Is data being sent between the right
  two objects?
• Are all the constraints and conditions from the
  requirement or use case being observed in this
  sequence diagram? Were the constraints observed?
  Was all of the behavior and data on the sequence
  diagram directly concerned with the requirement
  or use case?

56
Sequence diagram x Requirements and Use Cases
Text from Requirement/Use Case
- A customer, giving his account_number, asks for
an available parking spot to park his car. - To
get an available parking spot, the gas station
owner searches for the next available parking
place. - With this information the customer can
confirm the lease of the parking place. - The
time of payment (time of purchase or a monthly
paper bill) and how the service should be paid
(by cash, personal check or credit card) should
be given. - If the time of payment is the same
as the purchase time and Customer decides to pay
by Credit Card then Credit Card system should be
used. The Customer can only wait for 30 seconds
for the authorization process otherwise this
payment should made by cash or personal check to
avoid other Customers waiting on the lane. - It
allows the Gas Station Owner to mark a new
service purchase for this Customer at this date.
57
Sequence diagram x Requirements and Use Cases
Get an available parking spot
Pay by Credit Card
Discrepancy
58
Sequence diagram x Requirements and Use Cases

• Step 3 (cont.)
• Identify the behaviors described by the sequence
  diagram, and compare them with the description
  used on the requirement and use case. Do the
  objects exchange operations in the same specified
  order? Are all transported data in the right
  operations? Is data being sent between the right
  two objects?
• Are all the constraints and conditions from the
  requirement and use case being observed in this
  sequence diagram? Were the constraints observed?
  Was all of the behavior and data on the sequence
  diagram directly concerned with the requirement
  and use case?

59
Sequence diagram x Requirements and Use Cases
Text from Requirement/Use Case
- A customer, giving his account_number, asks for
an available parking spot to park his car. - To
get an available parking spot, the gas station
owner searches for the next available parking
place. - With this information the customer can
confirm the lease of the parking place. - The
time of payment (time of purchase or a monthly
paper bill) and how the service should be paid
(by cash, personal check or credit card) should
be given. - If the time of payment is the same
as the purchase time and Customer decides to pay
by Credit Card then Credit Card system should be
used. The Customer can only wait for 30 seconds
for the authorization process otherwise this
payment should made by cash or personal check to
avoid other Customers waiting on the lane. - It
allows the Gas Station Owner to mark a new
service purchase for this Customer at this date.
60
Sequence diagram x Requirements and Use Cases
Get an available parking spot
Pay by Credit Card
61
State Diagrams X Class Descriptions

• The Artifacts
• A set of Class Descriptions that lists the
  classes of the system along with their attributes
  and behaviors
• One or more State Diagrams that describe the
  internal states of an object and the possible
  transitions between states.
• The Goal
• To verify that the classes are defined in a way
  that can capture the functionality specified by
  the state diagrams.

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State Diagrams X Class Descriptions

• Step 1
• Inputs State Diagram
• Outputs Object States, transition actions
• General Instructions Understand the possible
  states of the object and the actions that trigger
  a state change.
• Specific Instructions
• Trace the sequence of states and the transitions
  and underline the name of each state.
• Highlight the transition actions.
• Think about how the actions and states fit
  together.

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State Diagrams X Class Descriptions
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State Diagrams X Class Descriptions

• Step 2
• Inputs Class Description, State Diagram (marked)
• Outputs Relevant object attributes and
  operations
• General Instructions Find the class, attributes,
  and operations on the Class Description that
  correspond to the state diagram.
• Specific Instructions
• Find the corresponding class or class hierarchy
  in the Class Description.
• Find out how that class encapsulates the states
  from the State Diagram.
• Are there any states on the state diagram
  that are not in the Class Description?

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State Diagrams X Class Descriptions
Discrepancy
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State Diagrams X Class Descriptions

• Step 2 (cont)
• For each transition action or constraint, verify
  that there are behaviors in the class that are
  capable of achieving it.
• Are all the actions encapsulated by the
  behaviors?
• Are all the constraints encapsulated?
• Is all of the data necessary to validate each
  constraint present?

67
State Diagrams X Class Descriptions

• Step 3
• Inputs Object States, Transition Actions
• Outputs Discrepancy Reports
• General Instructions Compare the Class
  Description and the State Diagram to make sure
  the class can capture the functionality.
• Specific Instructions
• Use your semantic knowledge of the class and the
  behaviors it should encapsulate to make sure that
  all of the states are described.

68
Sequence Diagrams X State Diagrams

• The Artifacts
• Sequence diagrams that describe the classes,
  objects, and possibly actors of a system and
  services they provide.
• One or more State Diagrams that describe the
  internal states of an object and the possible
  transitions between states
• The Goal
• To verify that every state transition for an
  object can be achieved by the operations of that
  object.

69
Sequence Diagrams X State Diagrams

• Step 1
• Inputs State Diagram
• Outputs Object States, transition actions
• General Instructions Understand the possible
  states of the object and the actions that trigger
  a state change.
• Specific Instructions
• Trace the sequence of states and the transitions
  and underline the name of each state.
• Highlight the transition actions.
• Think about how the actions and states fit
  together.

70
Sequence Diagrams X State Diagrams
71
Sequence Diagrams X State Diagrams

• Step 1
• Inputs State Diagram
• Outputs Object States, transition actions
• General Instructions Understand the possible
  states of the object and the actions that trigger
  a state change.
• Specific Instructions
• Trace the sequence of states and the transitions
  and underline the name of each state.
• Highlight the transition actions.
• Think about how the actions and states fit
  together.

72
Sequence Diagrams X State Diagrams
73
Sequence Diagrams X State Diagrams

• Step 1
• Inputs State Diagram
• Outputs Object States, transition actions
• General Instructions Understand the possible
  states of the object and the actions that trigger
  a state change.
• Specific Instructions
• Trace the sequence of states and the transitions
  and underline the name of each state.
• Highlight the transition actions.
• Think about how the actions and states fit
  together.

74
Sequence Diagrams X State Diagrams

• Step 2
• Inputs State Diagram, Transition Actions,
  Sequence Diagram
• Outputs Object Messages, Discrepancy Reports
• General Instructions Read the sequence diagram
  to understand how the transitions are achieved by
  the operations.
• Specific Instructions
• Choose the Sequence diagrams that contain the
  object from the State diagram
• Read the sequence diagram(s) to determine the
  system requirement being described.
• Think about which object states are semantically
  related to the system requirement. Mark these
  and use for the rest of the step.
• Map the operations from the Sequence diagram to
  the state transitions

75
Sequence Diagrams X State Diagrams
Get an available parking spot
Pay by Credit Card
76
Sequence Diagrams X State Diagrams

• Step 2
• Inputs State Diagram, Transition Actions,
  Sequence Diagram
• Outputs Object Messages, Discrepancy Reports
• General Instructions Read the sequence diagram
  to understand how the transitions are achieved by
  the messages sent.
• Specific Instructions
• Choose the Sequence diagrams that contain the
  object from the State diagram
• Read the sequence diagram(s) to determine the
  system requirement being described.
• Think about which object states are semantically
  related to the system service. Mark these and
  use for the rest of the step.
• Map the operations from the Sequence diagram to
  the state transitions

77
Sequence Diagrams X State Diagrams
Get an available parking spot
Which one is it???
78
Sequence Diagrams X State Diagrams

• Step 3
• Inputs Transition Actions, Object Messages
• Outputs Discrepancy Reports
• General Instructions Review the marked diagrams
  to make sure that all transition actions are
  accounted for.
• Specific Instructions
• Review the State Diagram and look for actions
  that were not matched with object operations from
  the Sequence Diagrams.
• If more than one transition action appears on the
  same Sequence diagram, make sure that they appear
  a correct order based on the State transitions.

79
Object Model and Classification Diagrams X Class
Descriptions

• The Artifacts
• An Object Model and Classification Diagram that
  describes the classes of a system and how they
  are associated.
• A set of Class Descriptions that lists the
  classes of a system along with their attributes
  and behaviors.
• The Goal
• To verify that the detailed descriptions of the
  classes contain all the information necessary
  according to the class diagram, and that the
  descriptions of the classes make semantic sense.

80
Object Model and Classification Diagrams X Class
Descriptions

• Step 1
• Inputs Object Model, Classification Diagram,
  Class Description
• Outputs Discrepancy Reports
• General Instructions Read the object model to
  understand the necessary properties of each
  object.
• Specific Instructions
• Make sure each object appears on the Class
  Description
• Make sure the name and textual description on the
  Class Description are meaningful.
• Make sure all attributes are described with their
  types.
• Make sure all the behaviors and constraints are
  described.

81
Object Model and Classification Diagrams X Class
Descriptions

• Step 1 (cont)
• Make sure all attributes are described with their
  types.
• Is the same attribute set present in both Class
  Description and Object Model?
• Does it make sense to put all these attributes
  together?
• Make sure all the behaviors and constraints are
  described.
• Is the same behavior set present in both Class
  Description and Object Model?
• Does it make sense to put all these behaviors
  together?
• Are all the constraints satisfiable using the
  attributes and behaviors in the class?
• Do the behaviors rely excessively on attributes
  of other classes?

82
Object Model and Classification Diagrams X Class
Descriptions
83
Object Model and Classification Diagrams X Class
Descriptions

• Step 1 (cont)
• Make sure all attributes are described with their
  types.
• Is the same attribute set present in both Class
  Description and Object Model?
• Does it make sense to put all these attributes
  together?
• Make sure all the behaviors and constraints are
  described.
• Is the same behavior set present in both Class
  Description and Object Model?
• Does it make sense to put all these behaviors
  together?
• Are all the constraints satisfiable using the
  attributes and behaviors in the class?
• Do the behaviors rely excessively on attributes
  of other classes?

84
Object Model and Classification Diagrams X Class
Descriptions
85
Object Model and Classification Diagrams X Class
Descriptions

• Step 1 (cont)
• Make sure any inheritance from the Classification
  Diagram is properly described in the Class
  Description
• Verify that all relationships are correctly
  described with respect to multiplicity
  indications
• Do object roles in Class Description and
  relationship notation on Object Model and Class
  Diagrams match?
• Do the relationships make sense, semantically?
• Are important cardinalities described in Class
  Description?
• Is the relationship between classes represented
  by an attribute in the Class Description?

86
Object Model and Classification Diagrams X Class
Descriptions

• Step 2
• Inputs Class Description
• Outputs Discrepancy Reports
• General Instructions Review the Class
  Descriptions for extraneous information
• Specific Instructions
• Make sure that all of the classes described in
  the Object Model and Classification Diagram
  appear on the Class Description.

87
Class Descriptions X Requirements

• The Artifacts
• A set of Requirements that describe the concepts
  and services necessary in the final system.
• A set of Class Descriptions that lists the
  classes of the system along with their attributes
  and behaviors.
• The Goal
• To verify that the concepts and services that are
  described by the functional requirements are
  captured appropriately by the class description.

88
Class Descriptions X Requirements

• Step 1
• Inputs Set of Requirements
• Outputs Candidate Classes/objects/attributes/serv
  ices, Constraints or Conditions on services
• General Instructions Read requirements to
  understand functionality
• Specific Instructions
• Read each requirement to understand the
  functionality described.
• Find the nouns, they are candidates to be
  classes, or attributes
• Find the verbs, or descriptions of actions, they
  are candidates to be behaviors or operations
• Look for descriptions of constraints or
  conditions on the nouns and verbs.

89
Class Descriptions X Requirements

• Requirements excerpt
• 9. If a customer wishes to reserve a parking
  spot he will provide his account number to the
  cashier. The cashier will use the system to
  search for an available spot. If an available
  spot is found, it will be marked as not
  available and returned to the cashier. The
  customer has the same options for paying for as
  parking spot as he does for paying for gasoline.
• 10. When the customer is finished with the
  parking spot, the cashier informs the system
  that the spot is available again.

90
Class Descriptions X Requirements

• Step 1
• Inputs Set of Requirements
• Outputs Candidate Classes/objects/attributes/serv
  ices, Constraints or Conditions on services
• General Instructions Read requirements to
  understand functionality
• Specific Instructions
• Read each requirement to understand the
  functionality described.
• Find the nouns, they are candidates to be
  classes, or attributes
• Find the verbs, or descriptions of actions, they
  are candidates to be behaviors or operations
• Look for descriptions of constraints or
  conditions on the nouns and verbs.

91
Class Descriptions X Requirements

• Requirements excerpt
• 9. If a customer wishes to reserve a parking
  spot he will provide his account number to the
  cashier. The cashier will use the system to
  search for an available spot. If an available
  spot is found, it will be marked as not
  available and returned to the cashier. The
  customer has the same options for paying for as
  parking spot as he does for paying for gasoline.
• 10. When the customer is finished with the
  parking spot, the cashier informs the system
  that the spot is available again.

92
Class Descriptions X Requirements

• Step 2
• Inputs Set of requirements, Class Descriptions
• Outputs Corresponding concepts on Class
  Descriptions and requirements, Discrepancy
  reports
• General Instructions Compare the Class
  Descriptions to the requirements to verify if the
  requirements were captured correctly.
• Specific Instructions
• For each action in the requirements, look for a
  corresponding (by name or by meaning) behavior in
  the Class Description
• For each noun, look for a class, set of classes,
  or attribute in the Class Description

93
Class Descriptions X Requirements

• 9. If a customer wishes to reserve a parking
  spot he will provide his account number to the
  cashier. The cashier will use the system to
  search for an available spot. If an available
  spot is found, it will be marked as not
  available and returned to the cashier. The
  customer has the same options for paying for as
  parking spot as he does for paying for gasoline.
• 10. When the customer is finished with the
  parking spot, the cashier informs the system
  that the spot is available again.

94
Class Descriptions X Requirements

• Step 2
• If the noun corresponds to a class
• Does the Class Description clearly describe the
  functionality associated with the noun?
• Are all the associated nouns encapsulated as
  attributes and the associated verbs encapsulated
  as behaviors?
• Are all the conditions and constraints that were
  described by the requirements captured in the
  Class Description?

95
Class Descriptions X Requirements

• Step 3
• Inputs Set of Requirements, Class Description
• Outputs Discrepancy Reports
• General Instructions Review the Class
  Description and Requirements to make sure that
  all appropriate concepts correspond between the
  documents.
• Specific Instructions
• Look for functionality that was described in the
  Requirements, but omitted from the design.
• Are there any nouns or verbs that were marked
  that are not included in the design but should
  be?

96
State Diagrams X Requirements and Use-Cases

• The Artifacts
• The set of all State Diagrams, one for each
  object
• A set of Requirements that describe the concepts
  and services that are necessary in the final
  system.
• The set of Use-cases that describe the important
  concepts of the system.
• The Goal
• To verify that the state diagrams describe
  appropriate states of objects and events that
  trigger state changes as described by the
  requirements and use cases.

97
State Diagrams X Requirements and Use-Cases

• Step 1 (For Each State Diagram)
• Inputs Requirements Description
• Outputs Object States, Adjacency Matrix
• General Instructions Read the requirements to
  determine the possible states of the object,
  which states are adjacent to each other, and the
  events that cause the state changes.
• Specific Instructions
• Find all requirements that this object
  participates in.
• Look for the states that are described in the
  requirements. (This can be an attribute value, or
  a combination of attribute values that cause the
  object to behave in a certain way.)
• Determine which state is the initial state

98
State Diagrams X Requirements and Use-Cases

• For Parking Spot State Diagram
• Requirements excerpt
• 9. If a customer wishes to reserve a parking
  spot he will provide his account number to the
  cashier. The cashier will use the system to
  search for an available spot. If an available
  spot is found, it will be marked as not
  available and returned to the cashier. The
  customer has the same options for paying for as
  parking spot as he does for paying for gasoline.
• 10. When the customer is finished with the
  parking spot, the cashier informs the system
  that the spot is available again.

99
State Diagrams X Requirements and Use-Cases

• Step 1 (For Each State Diagram)
• Inputs Requirements Description
• Outputs Object States, Adjacency Matrix
• General Instructions Read the requirements to
  determine the possible states of the object,
  which states are adjacent to each other, and the
  events that cause the state changes.
• Specific Instructions
• Find all requirements that this object
  participates in.
• Look for the states that are described in the
  requirements. (This can be an attribute value, or
  a combination of attribute values that cause the
  object to behave in a certain way.)
• Determine which state is the initial state and
  which is the end state.

100
State Diagrams X Requirements and Use-Cases

• For Parking Spot State Diagram
• Requirements excerpt
• 9. If a customer wishes to reserve a parking
  spot he will provide his account number to the
  cashier. The cashier will use the system to
  search for an available spot. If an available
  spot is found, it will be marked as not
  available and returned to the cashier. The
  customer has the same options for paying for as
  parking spot as he does for paying for gasoline.
• 10. When the customer is finished with the
  parking spot, the cashier informs the system
  that the spot is available again.

Initial State
101
State Diagrams X Requirements and Use-Cases

• Step 1 (cont)
• On a separate sheet of paper, create an NxN
  matrix, where N is the number of states
  identified in the requirements.
• For each pair of states, if the object can change
  from the state represented by the number on the
  left hand side, to the state represented by the
  number across the top, put a mark in the box. If
  you can determine what event causes this change,
  then put that event in the box.
• For any event written in the previous step, write
  down any constraints on that event described in
  the requirements.

102
State Diagrams X Requirements and Use-Cases
103
State Diagrams X Requirements and Use-Cases

• Step 1 (cont)
• On a separate sheet of paper, create an NxN
  matrix, where N is the number of states
  identified in the requirements.
• For each pair of states, if the object can change
  from the state represented by the number on the
  left hand side, to the state represented by the
  number across the top, put a mark in the box. If
  you can determine what event causes this change,
  then put that event in the box.
• For any event written in the previous step, write
  down any constraints on that event described in
  the requirements.

104
State Diagrams X Requirements and Use-Cases

• For Parking Spot State Diagram
• Requirements excerpt
• 9. If a customer wishes to reserve a parking
  spot he will provide his account number to the
  cashier. The cashier will use the system to
  search for an available spot. If an available
  spot is found, it will be marked as not
  available and returned to the cashier. The
  customer has the same options for paying for as
  parking spot as he does for paying for gasoline.
• 10. When the customer is finished with the
  parking spot, the cashier informs the system
  that the spot is available again.

Initial State
105
State Diagrams X Requirements and Use-Cases
106
State Diagrams X Requirements and Use-Cases

• Step 2
• Inputs Use Cases
• Outputs Completed Adjacency Matrix
• General Instructions Read the Use Cases to
  determine the events that can cause the state
  changes
• Specific Instructions
• Find the Use Cases that contain the current
  object
• For each box in the Adjacency matrix that is
  marked, examine the Use Cases and determine the
  event that causes the state change.
• For each box that is blank in the Adjacency
  Matrix, see if there is an event described in the
  Use Cases that could cause that change.

107
State Diagrams X Requirements and Use-Cases

• Step 3
• Inputs Requirements, State Diagram, Adjacency
  Matrix
• Outputs Discrepancy Reports
• General Instructions Read the State Diagram to
  determine if the states described are consistent
  with the Requirements and if the transitions are
  consistent with the Requirements and Use Cases.
• Specific Instructions
• Find each state marked in the Requirements on the
  State Diagram
• Are all the states from the Requirements
  represented in the State Diagram?
• Are there extra states on the State Diagram that
  were not described in the Requirements?

108
State Diagrams X Requirements and Use-Cases
Discrepancy
109
State Diagrams X Requirements and Use-Cases

• Step 3
• Compare the transition events marked on the
  Adjacency Matrix to the transition events on the
  State Diagram
• Are all of the events from the Adjacency Matrix
  present on the State Diagram?
• Are there extra events on the State Diagram?
• Find each constraint marked on the Adjacency
  Matrix on the State Diagram
• Are all of the constraints from the Adjacency
  Matrix described on the State Diagram?
• Are there extra constraints on the State
  Diagram?

110
State Diagrams X Requirements and Use-Cases
Discrepancy