INSE lecture 17 Standards Quality

SE-related Standards

Why?Who?What?

Why? “Things fitting together” People “talking the same language” Avoid duplication of requirements

statements & the preceding work

Joseph Witworth – Babbage’s Engineer

Who? – main players National bodies (BSI, AFNOR, DIN, etc) International Standards Organization International Electrotechnology Commission

– ISO/IEC JTC1 Military (UK, US, NATO etc) European Computer Manufacturers

Association (ECMA) IEEE IETF (for internet) W3C (for web)

What? - examples Character codes Floating point Internet & web Programming languages Project Management Quality

Quality in SE What do we mean by “Quality”? Some aspects of “Software Quality” ISO 9000

“Quality” – a muddled concept “degree of excellence, relative nature”

(Oxford Concise dictionary) Two conflicting concepts there:

excellence; relative nature

“Excellence” Top of some scale such as:

excellent very good goodOK bad very bad awful

But then we have to ask what each one of these means for a given kind of product…

“Know it when you see it”

“Relative nature” Easier to compare two products, and

as which is “better”… except that one might be better than the

other in one way, worse in another.

Production jargonTwo more senses:

Quality Control – finding out what level of defects we are producing

Quality Assurance – keeping the level of defects down to some acceptable level

Both are about “limiting defects” – I.e. an opposite sense to “excellence”

In practice, for SE… We seldom have a directly comparable

product, so “better/worse” will usually only apply to generalities;

“Excellence” will need a new definition for each new software product

But it is sensible to suggest a list of common defects

Aspects of SE excellence (1)From the user point of view: Correctness Usability ReliabilityAlso for safety-critical and security-critical

use: safety integrity

Aspects of SE excellence (2)From the managerial point of view: Extendability Scaleability Portability Conformance to Standards

Aspects of SE excellence (3)From the programmers point of view:

Readability / LearnabilityDebugabilityTestabiltyConformance to internal guidelines

ISO-9000 series of standards A set of generic standards covering quality

of anything – and in particular “Quality systems” for producing anything.

Some of them relate specifically to software – 9000-3 Guidelines for the application of ISO-9001

to the Development, Supply, and Maintenance of Software

9004-2 Quality Management and Quality System Elements, part 2

9126 Quality Factors

Management issues Needs managing sensitively, so that

staff are enthusiastic about “quality”despite the bureaucratic aspects being a

threat to morale…

After this lecture Standards and Quality are tough issues

to be passionate about – but professionalism says you need to be.

© C Lester 1997-2014