copyright 2003-2013, dennis j. frailey software engineering best practices – things you seldom...

Copyright 2003-2013, Dennis J. Frailey

Software Engineering Best Practices – Things You Seldom Learn Much About in School

Dennis J. FraileyACM Distinguished Speaker

[email protected]

This talk discusses several practices that make a big difference for real

software development projects


The Distinguished Speakers Program is made possible by

For additional information, please visit http://dsp.acm.org/

3 Copyright 2003-2013, Dennis J. Frailey 3

Objective

To present some basic techniques used in professional software development projects– Some of these are not widely covered in

academic computing programs


Would You Buy This Car?

The price is 50% more than what you agreed to pay

Delivered to the dealer 3 months late Not the right color Some of the options you selected aren’t

there (“we’ll install them later”) The speakers and the CD player are

incompatible, so you can only use the CD player through headphones

Although “new”, it has 5,000 miles on it from the extensive testing that was done

Despite that testing, it still won’t start if it’s below freezing and it has a number of other problems


Frequent Problems for Product Developers on Real Software Projects

Nobody knows what work must be done– Do we need to provide an

installation guide?– Is there a warranty on this

software? and what should we do about it if there

is?

– In what format should we deliver the code?

– Do we have to provide training for the end users?


Frequent Problems on Real Software Projects (continued)

Vague understanding of the big picture– Has the customer used a computer before?– How does the software fit into the overall

customer environment? Are the networks and computers suitable for the

software?

– How will the customer use the software?


Air Traffic Control Replacement System

The New System The Old System



Unclear understanding of how much has been accomplished and how much is left to do– “How much longer will it take?”– “How much more money is

required?”



Ignorance about risks– What are our biggest potential

project problems?– Do we have any idea what the

real risks are?– Do we know which ones to

worry about the most?– Can we mitigate the risks?

(make them less likely or lower their potential impact)

– Do we have a contingency plan? (what to do if the risks happen?



Confusion about different versions of software– Which version of the data base goes

with the latest version of the user interface?

– How come it does one thing in the customer’s site but something else in our testing lab?

– Does the design match the code? If not, which one is right?



Haphazard approaches to quality– “We didn’t have time to test it

thoroughly”– “We tested it for weeks but it still

had lots of bugs”


Best Practices for Managing These Problems

The Work Breakdown Structure– Documenting and organizing the work to be

done Estimating and Tracking

– So you know where you are Systems Engineering

– Designing the big system before designing the software

Risk Management Configuration Management Quality Assurance


The Work Breakdown Structure

Definition: A work breakdown structure is a hierarchical list of the work activities required to complete a project.

This includes tasks for: - Software development - Management of software development - Support of software development - Any other activities required to meet

customer requirements, such as:– creation of documents, – training programs, – tool development or acquisition, – travel, etc.

ParserCode

GeneratorFile

SystemRun TimeSystem

UserInterface

ManageSoftware

Development

Build “C”Compiler

Build TestSuite

WriteDocumentation

WriteInstallationSoftware

Software for“C” Compiler


Sample Work Breakdown Structure for Taking a Course

1. Take a Course on Programming in Java1.1 Do Assignment 1 – Simple Program1.2 Do Assignment 2 – Program with Arrays1.3 Take Midterm Exam1.4 Do Assignment 3 – Program with Pointers1.5 Do Assignment 4 – Program with I/O1.6 Take Final Exam

These are the tasks you must complete in order to finish the course


Sample Work Breakdown Structure

Hierarchy Allows Additional Detail

1. Take a Course on Programming in Java1.1 Do Assignment 1 – Simple Program 1.1.1 Study Chapters 1 and 2 of textbook 1.1.2 Write a Simple Java Program 1.2 Do Assignment 2 – Program with Arrays 1.2.1 Study Chapters 3 and 4 1.2.2 Review Graded Assignment 1 1.2.3 Write Java Program with Arrays1.3 Take Midterm Exam 1.3.1 Study Chapters 1-5 1.3.2 Meet with study group to review 1.3.3 Go to exam room at designated time


Sample WBS for a Software Project (top levels only)

1.0 Software for Payroll system 1.1 Build the Payroll software 1.1.1 Build a User Interface 1.1.2 Build a File System 1.1.3 Build a Data Base 1.1.4 Build a Table of Rules 1.1.5 Build a Check Printing System 1.2 Build the Test Suite for the Software 1.2.x (detailed steps for building test suite) … 1.3 Write Documentation 1.4 Write Installation Software 1.5 Manage the Above


The WBS Is ...

A “table of contents” for the project.


Top Level Role of WBS

SourceDocuments

(Statement of Work,

Requirements,contract,

test criteria, etc,)

HistoricalRecords(at end

of project)

WBS

CostEstimate

(proposal &/project start)

CostTracking(during

execution)


Using the WBS to Estimate

WBS #

Task Estimated Hours

Estimated Completion

1.1 Do Assignment 1 15 9/22

1.1.1 Read Chapters 1, 2 3 9/15

1.1.2 Write Simple Java Pgm 12 9/22


1.2.1 Read Chapters 3, 4 4 9/23

1.2.2 Review Graded Assign. 1 1 9/23

1.2.3 Write Java Program with Arrays

16 9/30


Using the WBS to Track

WBS #

Task Estimated Hours

Actual Hours

Estimated Completion

Actual

1.1 Do Assignment 1 15 12 9/22 9/25

1.1.1 Read Chapters 1, 2

3 2 9/15 9/22

1.1.2 Write Simple Java Pgm

12 10 9/22 9/25


1.2.1 Read Chapters 3, 4

4 9/23

1.2.2 Review Graded Assign. 1

1 9/23

1.2.3 Write Java Pgm with Arrays

16 9/30

When the project is over, you have a detailed record of how much time and effort were required.


Graph to Show Progress

I M Exhausted, CSE 7315, Fall 2004BCWS/ACWP/BCWP Line Chart

0

20

40

60

80

100

120

140

160

180

Wk 1 Wk 2 Wk 3 Wk 4 Wk 5 Wk 6 Wk 7 Wk 8 Wk 9 Wk 10 Wk 11 Wk 12 Wk 13 Wk 14 Wk 15

Week Number

Hou

rs

BCWS

ACWP

BCWP


Using the WBS for Historical Records

Previous WBS

New WBS

Facts about New

Project

Previous WBS

Previous WBS

Previous WBS

Old Projects

You can make more accurate estimates for the next project.


Systems Engineering

A Sample System

Display PrinterKeyboard

Processorand

Memory

SystemSoftware

PowerSupply

Computer

SystemUnit


Systems Engineering - Step 1 - Analyze the Requirements of the Total System

Determine what the customer really wants– >> Analysis of the problem and the

need Produce verifiable specifications

(specifications may be in the form of simulations of expected behavior, use cases, specification documents, system requirements models, or other things)

Confirm the specifications are right by conferring with the customer


Systems Engineering - Step 2 - Design the System

Determine the architecture of the system – >> Synthesis, not analysis– Done by Systems engineer and/or chief

architect Determine the major parts (functional

decomposition into sub-systems) Determine the interfaces between the

subsystems


Systems Engineering - Step 3 - Allocate the Requirements to the Components of the System

Determine what each part will do Assign requirements to each part based on what it is supposed to do

This is how you get some of the software requirements when software is part of a larger system


Typical Requirements Flowdown

Transmission

System Analysis& Design

Allocated Requirements

Automobile

Drive Train ChassisEngine

100 pounds

torque ...

50 pounds 2000 pounds

500 pounds250 hp

...

Original Requirements

3000 pounds

0-60mph in 9 sec


When the Product is FinishedVerify that it Satisfies the Requirements

Requirements

DevelopmentTesting or

Other Verification Methods

Verification Methods derived from requirements

When the requirements (specifications) are verifiable by

testing, you are much more likely to have effective tests


Ideal Requirements (some but not all desirable characteristics)

Cohesive (each requirement addresses

only one thing) Complete (each requirement is fully

stated; all requirements are known and allocated)

Sufficient (every required feature is specified)

Consistent (no requirements contradict each other)

Unambiguous (only one possible interpretation)

Verifiable (you can tell when they are met)


Actual Requirements

Some requirements will be:– TBD (unknown - to be

determined)– Wrong– Missing– Vague or unclear

Some requirements will

– Contradict others

– Not be readily verified

– Change in mid-stream

Technology changes

Customer understanding of problem changes

Problem changes


Risk Management for Imperfect Requirements

Define a lifecycle/process that is adaptable – it will readily accommodate requirements changes

Assign someone to be responsible to manage requirements changes– including involvement of software staff

Select a lifecycle based on level of expected requirements stability

Get ranges for “TBD” (to be determined) requirements

Work to eliminate wrong and missing requirements


Interface Requirements

How does your software interface with other parts of the system?

This is just as important as other requirements

Make sure the interface requirements are– Documented– Under Control

If possible, requirements should be – Contained in (or controlled by) a SINGLE

document or other control point


Who is Establishing the Requirements? All Stakeholders!

End user -- will use the software Champion -- will pay for it Marketing -- will sell it Accountants and Lawyers -- will protect

but may not understand the product or the process

Political factors– Such as engineers -- who “know better” than the

customer


“V” Model of Software DevelopmentA General Model of Software Development

Requirements Analysis

Architecture Design

Detailed Design

Implementation

Unit Test

Integration Test

Acceptance Test

Test Cases Based on Requirements

Test Cases Based on Architecture

Test Cases Based on Design

Test Planning Begins with Requirements!

Test Planning Begins with Requirements!

This model underlies almost all othersThis model underlies almost all others


Are we Asking the Right Question?

The usual question:– How can we verify the software (make sure we

have satisfied the requirements)?

A better question:– How can we define requirements that are readily

verified? The requirement can be verified through one of

these basic methods: inspection, demonstration, test (instrumented) or analysis (to include validated modeling &

simulation).


Risk Management

Risks are:– things that can go wrong

If it has already happened, or is certain to happen, it is an issue, not a risk!– You should be discussing your action plan

for managing the problem


Risk Management Phases

1) Risk Assessment – The things you do before you start the

project to identify– What can go wrong?– How it can hurt you?– How likely is it to happen?– Why it may happen?– How you can mitigate (reduce) the risk?

2) Risk Control– The things you do during the project

– Preventing the unexpected– Responding when you cannot prevent


Risk Assessment ChartRisk Evidence How

LikelyImpact Priority Mitigation

Late project due to employee turnover

Unplanned turnover rate has been running high

7 7 49 Employee bonuses if they stay to end of project

Bottleneck at testing due to changing require-ments

Past experience with this customer

8 6 48 Iterative development Customer workshops

Etc. Etc. Etc. Etc. Etc. Etc.


Risk Control

A) Risk Monitoring

- Watching to see if risks happen

– Metrics to warn you of problems

– Periodic reviews

B) Risk Abatement

- Counteracting risks

- Taking contingency actions as needed


Risk Control ChartRisk Monitoring Counteracting /

Contingency Ongoing

Mitigation

Late project due to employee turnover

Measure turnover rate and project schedule

Get management help in identifying alternate employees

Periodic employee mini-bonuses

Bottleneck at QA due to changing require-ments

Track requirements changes and QA backlog

Requirements freeze; Multiple releases

Feature prioritization

Etc. Etc. Etc. Etc.


Risk Management is Ongoing

Risk Management (planning, analysis)

Product Development

Data and reports to

identify and monitor risks

Actions to mitigate or abate risks


Example of Risk Monitoring:Requirements Stability Monitoring

Requirements Stability

0

20

40

60

80

100

120

140

160

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

TotalTBDChanges

CDRPDR


Setting Thresholds

Expected Range of Values

Abnormally High Values

Abnormally Low Values


Thresholds Help You Monitor Risks

Thresholds tell you when to act– Beware of the “contented frog” problem

– Historical experience is a good basis to judge when things are getting out of hand

It’s only a little hotter

than yesterday!


What Is Software Configuration Management?

Definition:

Software Configuration Management is the process

of identifying, organizing and managing modifications to

software

Software Configuration Management is the process

of identifying, organizing and managing modifications to

software


Purpose ofConfiguration Management

The purpose of configuration management is to maintain integrity of the product by controlling change to the

product

The purpose of configuration management is to maintain integrity of the product by controlling change to the

product


All components that make up or relate to a version of a product– The proper version of each:

What Is The Configuration?

� document� compiler used to develop� development tool� data set used for

simulating� special equipment� operating system

� test code� test data� library� procedur

e� hardware� etc.

� code module� component� data file� macro� simulator� specification� requirement

If any of the above is wrong, the product lacks integrity and may not work

If any of the above is wrong, the product lacks integrity and may not work


What is Integrity?

Having the right parts that all fit together to form a correct product.

Requirements

User’s Guide

Main, rel 2.3Sub1, rel 1.7Sub2, rel 3.1...

Object code


Why is SW Configuration Management Needed?

Because software is flexible, changeable, and intangible

It is too easy to lose integrity of software because of these factors

Unmanaged change is very possibly the largest single cause of failure to deliver

systems on time and within budget.NASA SCM Guidebook, August, 1995

Unmanaged change is very possibly the largest single cause of failure to deliver

systems on time and within budget.NASA SCM Guidebook, August, 1995


Examples of Loss of Integrity

Performance 2 years ago cannot be duplicated with the current release

Source code will not compile without errors

Compiled code will not execute with the same results as the released code

It worked in the factory but not in the field

All records of a particular feature are gone, and the programmer/designer left the company


More Examples of Loss of Integrity

Compiled code has different object code or code size from released code

A bug that we fixed once before has reappeared

Code does not match the design specification

A feature that we added and fully tested has suddenly stopped working

We cannot figure out which version of each module is needed to reproduce a problem we found in the field


Configuration Management Has Five Major Functions

1) Configuration Identification– A unique name for every version of every part– A record of which versions of the parts are combined

in what way to make a given release/version of the product [known as a Version Description Document]

2) Configuration Control– Rules for making changes to software

So two people don’t change it at the same time

3) Change Authorization– Deciding who is allowed to make changes and when?

4) Status accounting– Knowing where to find the current version of each

component?5) Configuration Authentication

– Verifying that everything is right


Software Quality Assurance

Purposes:

– To prevent defective products from being shipped to the customer

– To arbitrate disputes when there are debates about whether the product is “good enough”

– To provide managers and developers with visibility into the process being followed and the products being built So they can manage the outcome


Quality Assurance Looks at the Entire Process

Requirements

DevelopmentTesting and Inspection

PassFail

Standards ofQuality

Process and Design Standards

Tests derived from requirements


Software Quality Assurance

Typical Practices:

– Inspections

– Reviews

– Audits

– Communication

– Measurements

– Independent confirmation of compliance Standards, requirements, procedures


Professional Software Engineering Is ...

Building Software Systems that People can Rely On

“The application of a systematic, disciplined, quantifiable approach to the development, operation and maintenance of software; that is, the application of engineering to software.”

IEEE Standard Glossary of Software Engineering Terminology


Where Are The Computing Jobs?

Applications of Computers & Electronics to Problems

in Other Disciplines

Research Jobs

Systems Jobs (tool

development, operating

systems, etc.)All of

the Other

Jobs


What Kinds of Jobs does a Computing Graduate Do?

Write Software or Build Hardware Fix Bugs in Other Peoples’

Software/Hardware Test Software or Hardware Design Software or Hardware Understand Customers and Document Their

Requirements Design Systems to Solve Customer

Problems Control Changes to Software or Hardware Assure Quality in Software or Hardware Plan Software or Hardware Projects Manage Software or Hardware Projects

Care

er P

rog

ressio

n


Spectrum of Computing Jobs

Theory, Principles, Innovation

Application, Deployment,

Configuration

Computer Hardware

Organization; Information

Systems

Application Technologies

Software Methods &

Technologies

Systems Infrastructure

(Source: Computing Curriculum 2005, sponsored by ACM and IEEE Computer Society)





Configuration

Computer Hardware


Systems


Software Methods &

Technologies


Computer Engineer

Build Hardware that Works





Configuration

Computer Hardware


Systems


Software Methods &

Technologies


Software Engineer

Build Software that You Can Depend On





Configuration

Computer Hardware


Systems


Software Methods &

Technologies


Computer Scientist

Find New Ways to Solve Computing

Problems





Configuration

Computer Hardware


Systems


Software Methods &

Technologies


Information Systems

Design Computer Systems that Solve Organization Problems





Configuration

Computer Hardware


Systems


Software Methods &

Technologies


Information Technology

Build Computer Systems that

Solve Organizational

Problems


Some Things are Learned On the Job

Foundation Skills

Mathematics Science Communication

Computing Skills

Requirements Design Programming

Testing Management Planning

Application Skills

(depends on application area)

Job Experience

College Education


The Changes in Computing

1950’s 1960’s 1970’s 1980’s 1990’s 2000’s 2010’s

Hardware Technology

Vacuum Tubes

Transistors

I ntegrated Circuits

LSI VLSI ULSI Nano-systems

Programming Languages

Binary Assembly

Fortran Cobol

Pascal Algol Ada C Lisp

C++ GUI J ava

C# PhP XML

F#

Computing Paradigm

1 user Mainf rame

Batch Time Sharing

Personal Computer

LAN, WEB .NET ???

Operating System

none 1 user multi user multi user linked

networked Web, Open

source

Cloud

Data Base Methods

none Linear (tapes)

Hier-archical

Relational Object Oriented

X Query ???

Sof tware Design

pad and pencil

Flow Charts

Structured Design

Data Flow Object Oriented

RAD, XP, RUP

???


About ACM

ACM, the Association for Computing Machinery is the world’s largest educational and scientific computing society, uniting educators, researchers and professionals to inspire dialogue, share resources and address the field’s

challenges.

ACM strengthens the computing profession’s collective voice through strong leadership, promotion of the highest standards, and recognition of technical

excellence.

ACM supports the professional growth of its members by providing opportunities for life-long learning, career development, and professional

networking.

With over 100,000 members from over 100 countries, ACM works to advance computing as a science and a profession. www.acm.org


Questions?