Glossary


Laws of Software Evolution

A-B-C- D-E-F- G-H-I- J-K-L- M-N-O- P-Q-R- S-T-U- V-W-X- Y-Z

Identification

Laws of Software Evolution

Definitions/Uses

1996
Reference /Lehman, 1996a/ Laws of Software Evolution Revisited

Definition/
Use Laws of software evolution:
I-Continuing Change: (1974) E-Type systems must be continually adapted else they become progressively less satisfactory.
II-Increasing Complexity: (1974) As an E-type system is evolved its complexity increases unless work is done to maintain or reduce it.
III- Self Regulation: (1974) Global E-type system evolution processes are self-regulating.
IV-Conservation of Organisational Stability: (1978) Unless feedback mechanisms are appropriately adjusted, the average effective global activity rate in an evolving E-type system tends to remain constant over product lifetime.
V-Conservation of Familiarity: (1978) As an E-type system evolves all associated with it must maintain mastery of its content and behaviour to achieve satisfactory usage and evolution. Excessive growth diminishes that mastery and leads to a transient reduction in growth rate or even shrinkage. Therefore, the mean incremental growth remains constant or declines.
VI-Continuing growth: (1991) Functional content of E-type systems must be continually increased to maintain user satisfaction over lifetime.
VII- Declining Quality: (1996) Quality of E-type systems will appear to be declining unless they are rogorously maintained and adapted to operational environment changes.
VIII-Feedback System: (1996) E-type evolution process are multi-level, multi-loop, multi-agent feedback systems and must, in general, be treated as such to achieve major process improvement.

1996
Reference	/Lehman, 1996a/ Laws of Software Evolution Revisited
Definition/ Use	Laws of software evolution: I-Continuing Change: (1974) E-Type systems must be continually adapted else they become progressively less satisfactory. II-Increasing Complexity: (1974) As an E-type system is evolved its complexity increases unless work is done to maintain or reduce it. III- Self Regulation: (1974) Global E-type system evolution processes are self-regulating. IV-Conservation of Organisational Stability: (1978) Unless feedback mechanisms are appropriately adjusted, the average effective global activity rate in an evolving E-type system tends to remain constant over product lifetime. V-Conservation of Familiarity: (1978) As an E-type system evolves all associated with it must maintain mastery of its content and behaviour to achieve satisfactory usage and evolution. Excessive growth diminishes that mastery and leads to a transient reduction in growth rate or even shrinkage. Therefore, the mean incremental growth remains constant or declines. VI-Continuing growth: (1991) Functional content of E-type systems must be continually increased to maintain user satisfaction over lifetime. VII- Declining Quality: (1996) Quality of E-type systems will appear to be declining unless they are rogorously maintained and adapted to operational environment changes. VIII-Feedback System: (1996) E-type evolution process are multi-level, multi-loop, multi-agent feedback systems and must, in general, be treated as such to achieve major process improvement.

Publications on this area

Process Dynamics/Evolution/Change

Identification

Definitions/Uses

Publications on this area

See also