lectures 1a and 1b
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CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.1
Software Engineering: Analysis and Design - CSE3308
David Squire
Room 5.23A B Block, CaulfieldG12, Building 63, Clayton
9903 1033
(thanks to Martin Dick for initial development of course resources)
CSE3308/DMS/2001/2
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.2
Lecture Outline
Course Outline What is Software Engineering? Why Bother with Software Engineering? Product and Process The Software Development Lifecycle
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.3
Course outline
Objectives Assessment Passing the Subject Lectures, the lecturer and consultation Recommended reading Assignment Work Web Pages
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.4
Objectives
An understanding of analysis and design A knowledge of the difficulties of specifying
and producing large software products An awareness of the problems of managing
large software development projects A knowledge of the tools used to analyse and
design systems Some knowledge of modern commercial
software engineering practice
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.5
Assessment and Passing
This will consist of two components: An examination worth 40% of the marks Assignments worth 60% of the marks
There will be two practical assignments:
» A group project worth 45%
» An individual assignment worth 15%
You need to achieve 50% in both the exam and the assignments and achieve an overall mark of 50%, i.e.
You must get at least 20 marks out of 40 for the exam You must get 30 marks out of 60 for the assignments You must get 50 marks out of 100 overall
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.6
Lectures
Lectures will be held in lecture room S6 at 2:00pm on Wednesdays and C1 at 2:00pm on Thursdays
Notes for each week will be made available on the subject web page in PowerPoint and Postscript formats
At some lectures notes will be distributed, when student work on the notes is necessary
It is your responsibility to ensure that you have copies of all notes, including the assignments
All lecture material and assignment work is examinable
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.7
Lecturer and Consulation
Lecturer:
David SquireRoom 5.23A Building B - Caulfield campusEmail: [email protected] Phone: 9903 1033
Consultation times at Clayton campus: Wednesday 3pm - 5pm, building 63, room G.12 Thursday 3pm - 5pm, building 63, room
G.12
(note: these times may change - check subject web site)
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.8
Recommended Reading
There is no prescribed text. The following books cover the basic material in the course:
Booch, G., Rumbaugh, J., and Jacobson, I. The Unified Modeling Language User Guide (1998) Hargrave Library: 005.12 B724U
Yourdon, E.: Modern Structured Analysis (1989) Hargrave 004.21 Y81M
The lecture notes are long and detailed - the intent is to give you the material you will need
A list of further useful books is provided in your course outline
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.9
Assignment work
All work submitted by a group must be solely the work of that group
All work submitted by an individual must solely be the work of that individual
This is not to mean that you may not consult with others, but:
If you receive any help, you must specifically acknowledge that person in your
submitted work If any student or group of students submits work which is
not their own, they will be disciplined according to the University and Faculty policies - see the subject web site
Penalties range from exclusion from University to zero marks for the subject
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.10
Web pages
The subject web site can be found at:
http://www.csse.monash.edu.au/courseware/cse3308/
From week 2, information will include: Lectures (in Powerpoint and Postscript formats) Assignment specifications (in Microsoft Word and
Postscript formats) Links relevant to the subject
You should check the subject web site each week
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.11
What is Software Engineering?
Group Exercise
Break into groups of 4 or 5 (i.e. your neighbours, don’t move around the theatre)
Take 5 minutes to write down a definition of software engineering - this can be in point form
After 5 minutes, we will collect definitions from the class
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.12
What is Software Engineering?
Many Definitions “… the establishment and use of sound engineering
principles in order to obtain economically software that is reliable and works efficiently on real machines.” (Bauer 1969)
“The application of science and mathematics by which the capabilities of computer equipment are made useful to man via computer programs, procedures, and associated documentation.” (Boehm 1981)
“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 1993)
Designing, building and maintaining large software systems in a cost-effective way.
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.13
Why bother with Software Engineering?
Many very successful projects don’t use software engineering
examples - early Microsoft, Doom, Hotdog but they are often not repeatable
Many more projects fail because they don’t use software engineering. Failures occur because:
of the size of the project relative to previous efforts key personnel have left of failure to understand requirements the project delivers, but lacks the required quality of the introduction of new technology of many, many other reasons
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.14
Some classic disasters
CS90 - How Westpac wasted $250 million Therac 25 - Radiation death courtesy of the
computer McKinsey’s PeopleNet New Jersey Department of Motor Vehicles Microsoft’s first database - Omega Australian Customs Service - Intelligence
Gathering System Denver International Airport London Metropolitan Ambulance System
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.15
From E-Trade to E-Grave 3rd largest on-line
stockbroking service in the world
60,000 trades a day February 3rd - 75 minutes
downtime after slow access
February 4th - More downtime
February 5th - 29 minutes of downtime
Two class action law suits Stock price dropped from
US$62 to US$48
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.16
Some statistics
One in four systems miscarry 20% turnover in staff is not uncommon Major corporations have up to a 30 month
backlog Large systems take 3 to 5 years to develop Corporations are spending up to 20% of
revenue on Information Technology Year 2000 problem took up to 50% of
resources in at least one bank in Australia. Many of the systems were built in the 1980s
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.17
Product and Process
Both are key aspects in software engineering We move from an emphasis on product to
process, and back and forth Structured programming - Product Structured analysis and design - Process Data encapsulation (OO languages) - Product Capability Maturity Model/ISO9000 - Process Next step?
We need to be able to deliver quality software products to our customers with a consistent, well-managed and cost-effective process
Product and process are not a dichotomy
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.18
The Software Product
Is not the same as a hardware product Software is developed or engineered, it isn’t manufactured
like a personal computer Software doesn’t wear out Most software is custom-built, rather than being assembled
from existing components
A software product should perform the required function be reliable be maintainable be efficient have an appropriate user interface have an appropriate lifetime
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.19
A good software product?
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.20
The Software Product
Is composed of Programs Data Documentation
Two main types of product Generic - eg. Windows, Macintosh application software Bespoke - Systems created for specific application areas
Most software expenditure is generic Most software development effort is bespoke
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.21
The Software Process
The set of activities and associated results which produce a software product
The sequence of steps required to develop and maintain software
Sets out the technical and management framework for applying methods, tools and people to the software task
Definition: The Software Process is a description of the process
which guides software engineers as they work by identifying their roles and tasks.
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.22
Characteristics of a good process
Understandability Visibility Supportability Acceptability Reliability Robustness Maintainability Rapidity
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.23
Two questions
Is there a right process for software engineers to adopt?
Will having a good process guarantee a good product?
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.24
When do we need process?
We always have some process! The larger the project, the greater the need for
a formal process Complexity of building a system when related
to size is not linear.
Size EffortRequired
Errorsafter
releaseGigatron 5,000 1 25
Gigatron 2Deluxe
50,000 20 375 (15times
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.25
Determining Process
Several Schemes US Department of Defense use the Project
Formality Worksheet Projects rate between 12 (minimal formality)
to 60 (maximum formality) Most student projects are well under 20 and
require very minimal formal process to be successful
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.26
Steps in a Generic Software Process
Project Definition Requirements Analysis Design Program Implementation Component Testing Integration Testing System Testing System Delivery Maintenance
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.27
Process Activities (1)
Project Definition States the purpose of the project Makes initial decision on political and technical feasibility
of the project
Requirements Analysis High level definition of the functionality of the system,
primarily from the point of view of the users
Design Looks at the software requirements of the system and the
architecture of the system Lower level design activities - data structures, interface
representations, procedural (algorithmic) details
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.28
Process Activities (2)
Program Implementation Writing or generating the code to build the system
Component Testing Testing of the individual components while they are
being built and after they have been completed
Integration Testing Testing of the way individual components fit together
System Testing Testing of the whole system usually in concert with the
users (acceptance testing)
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.29
Process Activities (3)
System Delivery Implementation of the system into the working
environment and replacement of the existing system
Maintenance Corrective Adaptive Perfective
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.30
Types of Software Processes
Traditional/Waterfall Prototyping Rapid Application Development (RAD) Evolutionary
Incremental Spiral Component Assembly
Formal Methods Fourth Generation Techniques
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.31
The Waterfall ModelProject
Definition
System Delivery
Maintenance
Requirements Analysis
Design
Component Testing
Integration Testing
System Testing
Program Implementation
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Waterfall Model Most widely used Each step results in documentation May be suitable for well-understood
developments using familiar technology Not suited to new, different systems because
of specification uncertainty Difficulty in accommodating change after the
process has started Can accommodate iteration but indirectly Working version not available till late in
process Often get blocking states
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.33
Prototyping
Specifying requirements is often very difficult Users don’t know exactly what they want until
they see it Prototyping involves building a mock-up of
the system and using to obtain for user feedback
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.34
Prototyping
Listen to Customer
Build/ReviseMock-up
Customertest-drivesmock-up
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Prototyping
Ideally mock-up serves as mechanism for identifying requirements
Users like the method, get a feeling for the actual system
Less ideally may be the basis for completed product
prototypes often ignore quality/performance/maintenance issues
may create pressure from users on deliver earlier may use a less-than-ideal platform to deliver e.g Visual
Basic - excellent for prototyping, may not be as effective in actual operation
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.36
Rapid Application Development
Similar to waterfall but uses a very short development cycle (60 to 90 days to completion)
Uses component-based construction and emphasises reuse and code generation
Use multiple teams on scaleable projects Requires heavy resources Requires developers and customers who are
heavily committed Performance can be a problem Difficult to use with new technology
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.37
Rapid Application Development
Business
modelling
Data modelling
Process modelling
Application
generation
Testing and turnover
Business
modelling
Data modelling
Process modelling
Application
generation
Testing and
turnover
Business
modelling
Data modelling
Process modelling
Application
generation
Testing and
turnover
Team 1 Team 2 Team 3
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.38
Incremental Development
Applies an iterative philosophy to the waterfall model
Divide functionality of system into increments and use a linear sequence of development on each increment
First increment delivered is usually the core product, i.e only basic functionality
Reviews of each increment impact on design of later increments
Manages risk well
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.39
Incremental Development
analysis deliverydesign coding testing
analysis deliverydesign coding testing
analysis deliverydesign coding testing
analysis deliverydesign coding testing
1st Increment
2nd Increment
3rd Increment
4th Increment
Project Definition
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.40
The Spiral Model
Development cycles through multiple (3-6 task regions (6 stage version)
customer communication planning risk analysis engineering construction and release customer evaluation
Incremental releases early releases may be paper or prototypes later releases become more complicated
Models software until it is no longer used
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.41
Spiral Model
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Spiral Model
Not a silver bullet, but considered to be one of the best approaches
Is a realistic approach to the problems of large scale software development
Can use prototyping during any phase in the evolution of product
Requires excellent management and risk assessment skills
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.43
Component Assembly
Incorporates features of the spiral model Usually based on object technologies, but not
necessarily e.g Visual Basic Compose applications from pre-packaged
software components Can greatly boost productivity and reuse Relies heavily on quality and robustness of
the software components Fits into the Engineering/Construction task
region of the spiral model
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.44
Component Assembly
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.45
Formal Methods
Use of mathematical techniques to specify the requirements of the system e.g Z, VDM, Object-Z
Mainly used in life or mission-critical applications, e.g heart pacemakers, NASA
Can get very high quality software Problems
Time-consuming and expensive Few developers have necessary skills, so extensive
training required Difficult to use as a tool to communicate with users
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.46
Fourth Generation Techniques
The use of CASE and 4GL tools which let you specify the software at a high-level
Example: Hamilton-1 uses a formal specification language to generate complete system from requirements analysis ($100,000 per license)
Use of 4GT has grown considerably in the last decade
Some indications of productivity improvements for small and intermediate applications
CSE3308 - Software Engineering: Analysis and Design, 2001 Lecture 1A.47
Fourth Generation Techniques
Large projects require as much or more analysis, design and testing to achieve the time gains from the elimination of coding
Often problems with efficiency of automatically generated code