These are known as free-design parameters. When the range is finally obtained, the cycle begins again, based on perturbations of free-design parameters. Each program is "owned" and validated by a We have implemented a knowledge system that integrates the many computational programs (technology codes) Boeing aerospace vehicle designers use, thereby expediting design analysis. Because this system separates facts about attributes of the current set of technology codes from general knowledge about running the codes, those who maintain the system can keep it continuously up to date at low cost. The third approach left the technology codes untouched and built a procedural program that initiated separate, independent processes consisting of the technology codes communicating through a common database.

We have implemented a knowledge system that integrates the many computational programs ( technology codes) Boeing aerospace vehicle designers use, thereby expediting design analysis. Because this system separates facts about attributes of the current set of technology codes from general knowledge about running the codes, those who maintain the system can keep it continuously up to date at low cost. In contrast, three conventional approaches failed because they could not be maintained easily.

The third approach left the technology codes untouched and built a procedural program that initiated separate, independent processes consisting of the technology codes communicating through a common database. This was better because the technology organizations continued to maintain technical and managerial control over their codes. The rigid procedural integration program was still unacceptably costly to modify, requiring a flow time of approximately six weeks. However, it did provide a prototype and baseline for the knowledge system.