Program Families right Nancy Leveson, Sept. 1999 Basic premise: Software will inevitably exist in many versions Different services for slightly different markets Different hardware or software platforms Different resource tradeoffs(speed vs space) Different external events and devices Bug fixes Think of development as a tree rather than a line Never modify a completed program Always begin with one of intermediate forms Continue from that point making design decisions Order of decisions important in how far have to back ul Make early decisions only those that can be shared by all family members Put off decisions as long as possibleProgram Families Copyright c Nancy Leveson, Sept. 1999 Basic premise: Software will inevitably exist in many versions Different services for slightly different markets Different hardware or software platforms Different resource tradeoffs (speed vs. space) Different external events and devices Bug fixes Think of development as a tree rather than a line Never modify a completed program Always begin with one of intermediate forms Continue from that point making design decisions Order of decisions important in how far have to back up. Make early decisions only those that can be shared by all family members Put off decisions as long as possible. �