week01.ppt

CSE3308 - Software Engineering: Analysis and Design, 2003 Lecture 1.1

Software Engineering: Analysis and Design - CSE3308

David Squire

[email protected]

Room 5.23A B Block, Caulfield 9903 1033

101A, Building 26, Clayton9905 3295

(thanks to Martin Dick for initial development of course resources)

CSE3308/DMS/2003/3


Lecture Outline

Course Outline What is Software Engineering? Why Bother with Software Engineering? Product and Process The Software Development Lifecycle


Course outline

Objectives Assessment Passing the Subject Lectures, practice classes, the lecturer and

consultation Recommended reading Assignment Work Web Pages


Objectives (1) Knowledge of the difficulties of specifying and

producing large software products, leading to an appreciation of the need for software engineering

methodologies understanding of the distinction between software

engineering and programming, and thus the distinction between a software configuration and a program

An understanding of, and ability to apply, the methods of analysis and design, including:

structured analysis and design using Yourdon notation» Context Diagram, Event Lists, Data-Flow Diagrams,

Entity-Relationship Diagram, State Transition Diagrams, Process Specifications, Data Dictionary, Structure Chart

object-oriented analysis and design using UML» Use Cases, Class Diagrams, Interaction Diagrams, State

Diagrams, Package Diagrams, Activity Diagrams


Objectives (2)

Knowledge of , and the ability to apply, principles of user interface design such as affordances, awareness of mental models, visibility, mapping and feedback.

An awareness of the problems of managing large software development projects, and the techniques used to address them, including

Configuration management Software metrics Validation and verification techniques Quality management


Assessment and Passing

There are two assessment 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


Lectures

Lectures will be held at: 2:00pm on Wednesdays, room S6 2:00pm on Thursdays, room C1

Notes for each week will be made available on the subject web page in PowerPoint and Portable Document Format (PDF) formats

It is your responsibility to ensure that you have copies of all notes, including the assignments

All lecture material, worksheets and assignment work is examinable


Practice Classes There will be two practice classes each week:

12.00 noon to 2:00pm Thursday, room EH2 11:00am to 1:00pm Friday, room EH2

Students are expected to attend at most one practice class per week

During a practice class, students are expected to work on practice problems, or on their assignments

The lecturer and tutors will be available to comment on, and help with, solutions during the practice class.

Practice classes start in week 2


Lecturer and Consulation

Lecturer:

David SquireClayton, Bldg. 26, Room 101A, Ph. 9905 3295

(Wed., Thu, & Fri., 1st semester)Caulfield, Bldg B, Room 5.23A, Ph. 9903 1033 Email: [email protected]

Consultation The primary time for consultation is during the practice

classes Other consultation at Clayton campus (preferably by

appointment):Wednesday 3:15pm - 5pm, building 63, room

G.12


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)

Yourdon, E.: Modern Structured Analysis (1989) Pressman, R., Software Engineering: A Practitioner's

Approach, (2000)

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 the unit outline. Copies of these books are on reserve in the library.


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 unit web site

Penalties range from exclusion from University to zero marks for the subject


Web pages

The unit web site can be found at:

http://www.csse.monash.edu.au/courseware/cse3308/

Information at the web site will include: Lectures (in Powerpoint and PDF formats) Assignment specifications (in Microsoft Word and PDF

formats) Resources and links relevant to the subject Anonymous feedback forum

You should check the subject web site each week


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


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.


Why bother with Software Engineering?

Many very successful projects don’t use software engineering, e.g.

early Microsoft ID Software’s Doom Sausage’s 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


Some classic disasters

CS90 - How Westpac wasted $150 million Therac-25 - Radiation death courtesy of the computer McKinsey’s PeopleNet New Jersey Department of Motor Vehicles Microsoft’s first Windows database - Omega Australian Customs Service - Intelligence Gathering

System Denver International Airport London Ambulance Service


From E-Trade to E-Grave 3rd largest on-line

stockbroking service in the world

60,000 trades a day February 3rd, 1999 - 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


Some statistics

One in four systems miscarry 20% turnover in staff is not uncommon Major corporations have a backlog of up to a

30 months Large systems take 3 to 5 years to develop Corporations are spending up to 20% of

revenue on Information Technology Y2K problem took up to 50% of resources in

at least one bank in Australia. Many of the systems were built in the 1980s


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


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


A good software product?


The Software Product Is composed of

Programs Data Documentation

» requirements, analysis & design documents, walk-through minutes, test plan, user manuals, etc.

often referred to as the “software configuration” 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


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.


Characteristics of a good process

Understandability Visibility Supportability Acceptability Reliability Robustness Maintainability Rapidity


Two questions

Is there a right process for software engineers to adopt?

Will having a good process guarantee a good product?


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


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


Steps in a Generic Software Process

Project Definition Requirements Analysis Design Program Implementation Component Testing Integration Testing System Testing System Delivery Maintenance


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



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)



System Delivery Implementation of the system into the working

environment and replacement of the existing system

Maintenance Corrective Adaptive Perfective


Types of Software Processes

Traditional/Waterfall Prototyping Rapid Application Development (RAD) Evolutionary

Incremental Spiral Component Assembly

Formal Methods Fourth Generation Techniques


The Waterfall ModelProject

Definition

System Delivery

Maintenance

Requirements Analysis

Design

Component Testing

Integration Testing

System Testing

Program Implementation


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


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


Prototyping

Listen to Customer

Build/ReviseMock-up

Customertest-drivesmock-up


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


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


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


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


Incremental Development

analysis deliverydesign coding testing




1st Increment

2nd Increment

3rd Increment

4th Increment

Project Definition


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


Spiral Model


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


Component Assembly

Incorporates features of the spiral model Usually based on object technologies, but not

necessarily e.g. Visual Basic (older versions) 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


Component Assembly


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


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


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


References

Pressman, R., Software Engineering: A Practitioner's Approach, McGraw-Hill, 2000, (Chapters 1 and 2).

McConnell, S., Less is More: Jump-Start Productivity with Small Teams, Software Development, October 1997, pp. 28-34.http://www.stevemcconnell.com/articles/art06.htm

week01.ppt

Documents

software configuration

practice classes

submitted work

assignment work web

software development

class diagrams

practice problems

subject web site