CSC302H1 Lecture 4: 2014.01.16
Document Summary
Program types, defined by lehman: s-type programs specifiable. Problem: the problem can be state formally and completely. Acceptance: is program correct w. r. t its specifications. A new specification = defines a new need new program. Lehman"s laws of program evolution (e-type programs only: 1. Continuing change any software that reflects some external reality undergoes continual change or becomes progressively less useful. Change continues till replacement is more cost effective: 2. Unless steps are taken to control it: 3. Fundamental law of program evolution software evolution is self-regulating w/ statistically determinable trends and invariants. Program evolution is composed of several attributes that are dynamically related such that the change in one alters others (through feedback) and tends toward a goal: 4. Conseration of organizational stability during the active life of a software, the work output of a development project is roughly constant regardless of resources: 5. Conservation of familiarity the amount of change in successive releases is roughly constant.
