Transcript Active Design Reviews

Active Design Reviews
Doug Paida
Roy Mammen
Sharan Mudgal
Jerry Cheng
Overview
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What is design review?
Taxonomy
Limitations of Conventional approach
Walking through the Active Review
Process using an example
Conclusions
What is a design review?
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A process of identifying faults in the
design of a software program
Review should uncover both errors made
in producing design documents, and errors
made earlier in the design process
Taxonomy
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Structured Walkthrough
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author of the design and one or more other
developers familiar with the development
activity are involved
Code Reading
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two or more developers read the code
independently
Discuss with the author
Taxonomy
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Code Inspection
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The process definition included planning, preparation
, inspection, rework and follow up with specific roles
define for the participants
author/reader paraphrases the material, while the
participants ask question that may lead to the
discovery of defects
Software Review
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The reviewers go through the material individually
using a checklist
The author collects the checklists and consolidates
the results.
Taxonomy
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Active Design Review
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The questionnaire focuses the reviewer's attention on a
particular set of issue
reviewers concentrate on different sets of issues.
The author meets with the reviewers individually to review their
findings.
Defect-Based Reading
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possible defects in requirements documents
For each defect class a set of questions was developed that
would characterize the defect class
The questions also characterize a set of steps that should be
performed while reading called scenarios.
the reader tries to answer the questions provided in the scenario.
Taxonomy
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Meetingless Reviews
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As effective as meeting-based ones
Individual strategies find more issues to resolve but
these have a higher false positive and duplication
rates
The duplication rates can be reduced by specializing
the roles during the process.
Computer-mediated Technical Reviews
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supporting clerical functions of distribution and defect
report collection and rework tracking.
Aimed at synchronous distributed reviews where the
review is not required to be in the room.
Limitations of Conventional approach
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Too much information to go through, and
not enough time to do it thoroughly
Unfamiliarity of individual reviewers with
the overall goals of the design
No single part of the design gets a
thorough and complete evaluation
(continued)
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Burden is on reviewer to initiate action
One-on-one interaction between individual
reviewers and design team is limited
No systematic procedure – generally more
free-form type of format
Active Design Review Process
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Change from “general” review to a set of
more focused reviews
Use questionnaires to actively engage the
reviewer in using the design
More opportunities for one-on-one
discussion between reviewer and designer
A design example
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We have been asked to review a design for a
module which is part of an order processing
system for a hospital.
The order processing system allows users to
order items for patients, such as tests or
medications.
The module we are reviewing acts as an
interface between the order database and
other modules in the system, hiding details of
the actual database tables used.
Design Example (cont.)
Order Processing System
Add/Cancel Order
Print/Display Orders
Orders
Order
Item
Database Interface
Database
Module requirements
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An order must contain at least these data items:
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Patient ID
List of items being ordered. There must always be at
least one item in every order.
Date/time the items are being ordered for
Status of the order (active or cancelled)
An item in an order contains these data items:
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Item ID
Quantity ordered
Module requirements
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Basic functionality required
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Add a new order for a patient
Change an order’s status to “cancelled”
Obtain the number of orders a patient has
Iterate through all orders for a patient
Iterate through all items within an order
Module requirements
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Actions that should be prohibited
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Making order active again once it is cancelled
Adding items to an order after it’s been
posted to the database
Module specification
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Data in the Order class
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int patientID
int orderID
Date orderDateTime
int status
Vector items
Module specification
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Access functions for Order class
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void addItem(Item i)
Item getFirstItem()
Item getNextItem()
int numItems()
void setStatusToCancelled()
Date getOrderDateTime()
int getStatus()
Module specification
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Data for Item class
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int itemID
int quantity
Access functions for Item class
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int getItemID()
int getQuantity()
Module specification
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Access functions for Orders class
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void submitOrder(Order o)
void updateOrder(Order o)
Order getOrder(int orderID)
Order getFirstOrder(int patientID)
Order getNextOrder()
int numOrders(int patientID)
Module specification
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Undesired Events
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getNextOrder() called before getFirstOrder()
addItem() called on an order that’s already
been posted to the database
Steps for Active Design Review
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Prepare design and documentation for
review
Identify for specialized reviews
Identify the reviewers needed
Design the questionnaires
Conduct the review
Active Design Review Process
Step 1: Prepare the design for review
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Think about what criteria reviewers will use:
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Well-structured
Simple
Efficient
Adequate
Flexible
Practical
Implementable
Standardized
Active Design Review Process
Step 1: Prepare the documentation for review
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Make assumptions explicit
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Module can record the order pertaining to a patient.
It is possible to obtain all the orders for a patient.
Module can determine & change the status of an
order.
The order always contains at least one item
The status of an order is always in one of the two
states i.e active or cancelled.
Active Design Review Process
Step 1: Prepare the documentation for review
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Incorrect Usage Assumptions (UE)
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Cannot add or remove items once the order is
placed.
Once an order is cancelled, the status cannot
be set to active again.
An item is always added with respect to an
order.
Active Design Review Process
Step 2: Identify the specialized reviews
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Focus the reviewer’s attention on specific
properties of the design
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Data Access Sufficiency.
Provides all data required by the other modules ?
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Assumption Sufficiency.
Contains all assumptions needed by the user program to efficiently
access the DB ?
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Consistency between Assumptions and Functions.
Assumptions? Access Functions? UE?
Active Design Review Process
Step 3: Identify the reviewers needed
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People with different perspectives and
expertise are needed as reviewers
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Programmers and analysts who worked on
the other modules in this order processing
system.
Programmers and analysts familiar with
hospital information systems in general.
Active Design Review Process
Step 4: Design the questionnaires
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Make reviewers take an active role
Make them use the documentation
Phrase questions in an active way
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“Write down the exceptions that can occur”
rather than “Are exceptions defined for every
program?”
Active Design Review Process
Step 5: Conduct the review
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Present an overview of the module
Assign reviews to reviewers
Reviewers complete their reviews, meeting with
designers as needed
Designers review completed questionnaires, and
meet with reviewers to resolve questions
Designers produce new version of the
documentation
Sample Review: Data Access Sufficiency
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the access functions should be evaluated to ensure that
access is provided to all data required by the other
modules
piece of data about an order that cannot be retrieved
through an access function but needed reflects error in
design.
possible to modify the value of any piece of data in
violation of the stated requirements, then there is a
design error.
The module specifications should be reviewed by
programmers of the other order processing system
modules for their ability to satisfy these criteria.
Example Questionnaire
The following questions should be used to aid in
this review
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Using the access functions provided in the module
specification, write the code you would use to obtain
the date/time, item number and quantity ordered for
all active orders for a patient.
Attempt to come up with a sequence of access
function calls that would allow a program to set a
cancelled order’s status to active.
For each access function provided, write down the
specific requirements from the requirements list that
you believe the function was designed to meet.
Make note of any functions that do not appear to
satisfy any specific requirements
Conclusions
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Reviewers focus on those areas they are best
suited to evaluate
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Time is used more wisely for all participants
More errors are likely to be found
One-on-one communication with designers
makes it easier for people to speak up
Few errors found not necessarily indicate that
the design is good, but that the review process
was not as effective as it could have been