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
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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.

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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
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
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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
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(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
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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
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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 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.

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Sequence diagram x Requirements and Use Cases
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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