introduction to se

8/2/2019 Introduction to SE

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AN INTRODUCTION TO SOFTWARE

ENGINEERING

PresenterAmbili P K


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Objectives

Understand what Software Engineering is,and why it is important

Answer fundamental questions aboutSoftware Engineering

Introduce ethical and professionalresponsibility issues as they relate tocomputer scientists and software engineers


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Questions about Software

Engineering What is software?

Software includes source code, executable, andassociated documentation such as requirementsdocuments, design models, and user manuals

May be targeted for some general purpose (webbrowser, word processor, etc), or for a specificcustom need

New software can be produced from scratch, byconfiguring generic software systems, or byreusing existing software


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Engineering What is Software Engineering?

Software engineering is an engineering disciplinethat applies theories, methods, and tools to solveproblems related to software production andmaintenance

Software engineers strive to deliver high-qualitysoftware, on time and within budget


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Engineering Why is Software Engineering Important?

Financial, security, and safety critical systems relyon software

Software mediates every aspect of our Internetexperience

The economies of all developed nations are

dependent on software There is an increasing need to cost effectively

develop high-quality software


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Engineering What is the difference between Software Engineering

and Computer Science?

Software engineering is concerned with producingusable software for today; computer science is

concerned with finding fundamental truths abouttheoretical problems for posterity

Software engineering projects have fixed budgetsand schedules; computer science projects haveopen-ended budgets and schedules

Software created by software engineers mustevolve as users needs change; solutions createdby Computer Scientists never change


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Engineering What is the difference between Software Engineering

and Computer Science?

Software engineers require domain knowledge tofunction; computer scientists rely on

mathematical principles to function Unlike physics and electrical engineering,

software engineers often rely on methods andprinciples borrowed from other engineeringdisciplines instead of computer science


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Engineering What is the difference between Software

Engineering and System Engineering? System Engineering is concerned with all aspects

of computer based systems, including hardware,software and process engineering; applies testedand known principles; the discipline is thousandsof years old

Software Engineering is concerned with

developing the software infrastructure, control,applications, and databases in the system; oftenapply new and untested elements in softwareprojects; the discipline is about 50 years old


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Engineering What is a Software Process?

A software process is a set of activities and theiroutput, which result in a software product

Four fundamental process activities are: Specification: Defines what the software should do, and its

operational constraints

Design and implementation: Designs the solutions, andproduces the source code to meet the specification

Validation: Checks that the software produced is what thecustomer wants

Evolution: Changes made to the software that meet userschanging needs


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Engineering What is a Software Process model?

An abstract representation of a software process,presented from a particular perspective; for

example, workflow (sequence of activities), data-flow (information flow), or role/action (who doeswhat)

These process models explain different

approaches to software development; forexample, Waterfall, Iterative, and ComponentBased Software Engineering


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Engineering What is the cost of Software?

Software costs often dominate computer systemcosts.

Software costs more to maintain than to developfrom scratch. The maintenance costs for systemswith a long-life, may be several times itsdevelopment costs


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Engineering What are the costs of Software Engineering?

Roughly 60% of costs are development costs, and40% are testing costs. Evolution costs often

exceed development costs in custom software Costs vary depending on the type and

requirements of system under development

The distribution of costs depend on the

development model used


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Engineering What are Software Engineering methods?

Structured approaches to software development, including:

Model descriptions: Describes graphical models (i.e.object, data-flow, state machine models, etc)

Rules: Constraints applied to system models (i.e.entities must have unique names)

Recommendations: Best practices for designingsoftware (i.e. include no more than nine processes in

a data flow diagram) Process guidance: what activities to follow (i.e.

document object attributes before defining itsoperations)


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Engineering What is CASE?

Computer Assisted Software Engineering, used toprovide automated support for software process

activities

Often used for method support

Upper-CASE tools support requirements

gathering and design activities Lower-CASE tools support implementation,

debugging, and testing activities


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Engineering What are the attributes of good software?

Software should deliver the functionality requiredby the user. In addition, it should deliver non-

functionalrequirements such as:

Maintainability: Must be easy to evolve to addresschanging needs

Dependability: Must be trustworthy

Efficiency: Should not waste system resources

Acceptability: Users must be able to use thesoftware


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Engineering

What are the key challenges facing softwareengineering? Heterogeneity: How to build software that works

on different platforms, that can integrate witholder legacy systems which are written in differentprogramming languages

Delivery: How to shorten the time it takes to

deliver a finished software product, withoutcompromising its quality

Trust: How to develop techniques to demonstratethat software can be trusted by its users


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Professional and Ethical

Responsibility

Software engineering involves widerresponsibilities than just the application oftechnical skills

Software engineers must behave in honestand ethically responsible ways to berespected as professionals

Ethical behavior is more than simplyupholding the law


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Issues of Professional

Responsibility

Confidentiality

Always respect confidentiality of employers orclients, even when there is no formal

confidentiality agreement

Competence

Never misrepresent ones level of competence.

Never accept work beyond ones level ofcompetence


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Issues of Professional

Responsibility

Intellectual property rights

Ensure that the intellectual property of employersand clients is protected

Be aware of local laws governing use ofintellectual property such as patents andcopyright

Computer misuse Never use technical skills to misuse other peoples

computers


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ACM/IEEE Software Engineering Code

of Ethics and Professional Practice

The commitment of software engineers tomake their discipline a respected profession,and to adhere to the eight principles for the

health, safety, and welfare of the public.


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Code of Ethics Eight

Principles

Public: Software engineers shall act consistently with the

public interest.

Client and Employer: Software engineers shall act in a manner that is in

the best interests of their client and employerconsistent with the public interest.

Product: Software engineers shall ensure that their

products and related modifications meet thehighest professional standards possible.


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Principles

Judgment:

Software engineers shall maintain integrity andindependence in their professional judgment.

Management:

Software engineering managers and leaders shallsubscribe to and promote an ethical approach to

the management of software development andmaintenance.


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Principles

Profession: Software engineers shall advance the integrity

and reputation of the profession consistent withthe public interest.

Colleagues: Software engineers shall be fair to and supportive

of their colleagues.

Self: Software engineers shall participate in lifelong

learning regarding the practice of their professionand shall promote an ethical approach to thepractice of the profession.

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