Some notes for Software Engineering

by Herbert J. Bernstein
© Copyright 1999, 2002 Herbert J. Bernstein

Quality Issues

Software has a notorious reputation for poor quality. It is important to focus on the issues which relate to quality in all aspects of software engineering.

Quality and Systems

• Software is the result of the operations of software development systems
• Software can be a component of a system affecting the quality of its operation and products
• A system may be said to be of high quality when there is a high probability that the system will perform in the desired manner or produce the desired product.
• Quality may be tangible, quantifiable and measurable
  • Mean time between failures (MTTF), mean time to repair (MTTR), errors per line of code, errors per correction cycle, ...
  • Standards, control theory, feedback, loops, measurement, ...
• Quality may not be quantifiable and may not be measurable
  • a "comfortable" user interface, an aesthically pleasing GUI.
  • attempt to quantify the unquantifiable by measuring human reactions.
• Quality issues may result from system failures
• Quality issues may result from human error
• Quality control (QC) -- adjustments to controls of a system to keep the performace and products of a system in conformance with standards
  • Requires measurements within the system as it operates
  • Requires that adjustments and corrections be made before a "bad" result is produced
  • Many systems achieve optimal control with "bang-bang" control
• Quality assurance (QA) -- measurement of the performance and products of a systems to assure that the results conform to standards, and rejection of performance or products that do not conform.
  • Only workable when a the system produces a signficant number of acceptable results
• Total Quality Management (TQM)
  • Formalized in the U.S. Air Force by William Creech, "The Five Pillars of TQM: How to make Total Quality Management Work for You"
    • Product -- breaking rocks vs. building a cathedral
    • Process -- quality is needed in all processes that create products
    • Organization -- organize small
    • Leadership -- as opposed to management
    • Commitment -- on all levels, must be fostered, rewards for achieving desired results
  • Measure quality by results delivered to customers
  • All members of the organization participate
  • Problem solving crosses functional and hierarchical boundaries
  • Flattens hierarchies
  • Self-managed (leaderless) work-team oriented
  • Drives decision making down the hierarchy to the line
  • See http://www.hrzone.com/topics/tqm.html "Total Quality Management, An Overview," by Judith Ann Schlenker
• Software Capability Maturity Model (SEI SW-CMM)
  • See http://www.sei.cmu.edu/cmm/cmm.html
  • Defines 5 levels of software process maturity
    1. Initial -- ad hoc processes
    2. Repeatable -- able to do similar projects succesfully
       • Project management processes in place to track cost, schedule and functionality
       • Special attention on Requirements Management, Software Project Planning, Software Project Tracking and Oversight, Software Subcontract Management, Software Quality Assurance, and Software Configuration Management
    3. Defined -- documented processes in place
       • Organization has a standard software process
       • Management and engineering activities documented and standardized
       • All projects use an approved tailored version of the standard
       • Special attention on Organization Process Focus, Organization Process Definition, Training Program, Integrated Software Management, Software Product Engineering, Intergroup Coordination, and Peer Reviews.
    4. Managed -- software process and product are measured, qualitatively understood and controlled
       • Special attention on Quantitative Process Management and Software Quality Management.
    5. Optimizing -- continuous process improvement using feedback from processes and using pilot efforts
       • Special attention on Defect Prevention, Technology Change Management, and Process Change Management
• ISO 9000
  • See http://www.praxiom.com/
  • A set of process standards
  • Attempts to provide a common definition of "quality"
  • Based on systems-oriented, customer-oriented approach:
    • Focus on customers
    • Leadership
    • Involve everyone
    • Process oriented
    • Systems oriented
    • Continual improvement
    • Make desions based on facts
    • Maintain relationship with suppliers
  • Used to be very documentation oriented (in practice sufficient for CMM level 2 or 3)
  • Now based on development, documentation, implementation, monitoring and improvement of each system process (should bring up to CMM level 4 or 5)