CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 1 SMU CSE 8314 / NTU SE 762-N Software Measurement and Quality Engineering Module 07 Attributes of a Quality Product, Part 2

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 2 Attributes of a Quality Product Reliability Maintainability Verification Validation Testing and Evaluation Safety Supportability

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 3 Attributes of a Quality Product Safety

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 4 Safety A product is safe if it will not cause harm This may be hard to test Human factors often play a big part Software safety must be evaluated from the perspective of the system that the software is a part of – e.g. safety issues in a word processor vs. an aircraft system

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 5 Software Safety Seldom addressed in Computer Science programs But today, product problems are more and more being attributed to software, and more of this is likely. This subject is covered in more depth in other SMU courses

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 6 Software Liability The day may soon come when product liability is attributed to software developers. Consider the software that controls a nuclear reactor. Who will be liable if it fails and causes a major disaster?

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 7 Principles of Professional Software Development These are still emerging They are needed before software engineering can be considered a professional discipline

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 8 Is a Software Engineer an Engineer? It is illegal in many states to call yourself a software engineer unless you are a registered (licensed) professional engineer Several countries and at least one US State now license software engineers as professional engineers

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 9 Is a Software Engineer an Engineer? CSAB/ABET has begun to accredit software engineering academic programs IEEE has introduced a certification program for software developers ASQ has a certification program for software quality engineers ACM and IEEE have endorsed a software engineering code of ethics

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 10 Software Engineering Body of Knowledge IEEE Computer Society and eleven other sponsors have developed SWEBOK - a “guide” to the software engineering body of knowledge This guide is being used to define software engineering curricula in industry and academia

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 11 In Short... The time is coming when software development professionals will be expected to adhere to recognize standards, to utilize accepted practices, and to know basic facts about their discipline The attorneys are educating themselves about these matters – Which means there will soon be legal implications for unsafe software

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 12 Attributes of a Quality Product Supportability

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 13 Supportability Can it be readily supported? Can the software be updated (in the field)? Can the software be examined to determine its release, version, contents, etc.? Can the software be evaluated? Can the software be tested? etc.

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 14 Supportability has Design Implications Providing access to the software – Data paths – Interfaces – Modes of operation that permit access Providing a means of modifying – ROM vs. RAM – Memory loading & verification/validation Organizing to facilitate upgrades – How are the components combined?

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 15 Design for Supportability: Background for Example With defense systems (and most major commercial systems) you must designate individual “configuration items” or “products”. Each configuration item is a stand- alone element that has its own price, its own part number, perhaps its own contract, and requires its own documentation, maintenance procedures, etc.

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 16 Background (2 of 3) Example: on a PC, the software configuration items might be the operating system, word processor, spreadsheet, database, and such. Alternate example: you could “bundle” the above into one configuration item - but that would mean you cannot upgrade the spreadsheet without upgrading all the others.

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 17 Background (3 of 3) Alternate example: you could “unbundle” the spreadsheet into the user interface, macro processor, arithmetic processor, and other parts – But this would be needlessly complex and expensive for the customer. Selection of configuration items is a major decision when designing a software system.

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 18 Design for Supportability IFF System Example Function: respond to a signal and identify yourself as a “friend” Application: used on military vehicles in a combat zone to guard against accidental attack by “friendly fire” IFF System Identify yourself! Friend or Foe? Friend -- Here’s the Password xxxxx Platforms: Airplanes -- All services, primarily USAF Ships -- US Navy Tanks, ATVs, etc. -- US Army

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 19 Basic Architecture of IFF System Common to All Platforms Interfac e (unique to each platform) Use of common elements saves money in development, testing and production

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 20 Basic Design of IFF Computer System RAM (fast, but loses contents when powered down) Low Speed ROM (large, low cost, slow) Note: Three separate memory systems Software is distributed as ROM memory chips I/ O I/F CPUCPU download at power up HIGH SPEED ROM (small, costly, read-only, but retains contents)

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 21 Three Versions of the Product ROMROM RAMRAM ARMY VERSION AIR FORCE VERSION NAVY VERSION I/F COMMON I/F

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 22 How to Partition the Software? Option 1 Three Configuration Items: Most of the software is common – saves money

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 23 Issues with Option 1 Supportability Problem: – Changing the common portion of any one version requires changing (and re- testing) the other two -- or else losing the commonality Also: An upgrade requires changing two memory components - more costly

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 24 Option 2 Four configuration items: Can avoid requiring separate memory chips for common and interface by having a single chip contain two configuration items: – Common plus selected interface

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 25 Issues with Option 2 Problem: – A change in the ROM part requires a change in the RAM part as well (and vice versa) – Must replace two memory components. Also – Two configuration items on one chip causes complications in paperwork

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 26 Option 3 Six configuration items: – ROM & RAM part for each service

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 27 Issues with Option 3 Problem: – Not a logical approach from a software design perspective – A change to any one version requires re- testing the common part – You still have paperwork problems But it is probably the most logical from a supportability perspective

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 28 Option 4 Eight Configuration Items:

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 29 Issues with Option 4 Many parts to stock and keep straight Excessive documentation cost Marginal if any benefit over option 3

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 30 An Additional Problem Military (and corporate) standards and policies generally dictate certain kinds of documentation, review processes, etc. for each configuration item. In order to avoid excessive cost, program managers often decide arbitrarily on a small number of configuration items.

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 31 A Preferred Approach Select the right number of configuration items and tailor out unnecessary documentation, reviews, etc. But that takes knowledge, time, preparation, planning, etc. -- i.e., MATURITY

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 32 Summary There are many attributes associated with product quality Each of these attributes requires effective planning and analysis But addressing these elements results in significant improvements in quality and savings in long term cost These must be addressed in the context of how people function and how people fail

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 33 References Marciniak and Evans. Software Quality Assurance and Management. Schulmeyer, G. Gordon and James McManus. Handbook of Software Quality Assurance, Second Edition. Van Nostrand Reinhold, New York, ISBN

CSE SW Measurement and Quality Engineering Copyright © , Dennis J. Frailey, All Rights Reserved CSE8314M07 version 3.09Slide 34 END OF MODULE 07