Balance between optimistic planning and pessimistic planning in a mission critical project

This paper considers an issue of a balance between the optimistic planning and the pessimistic planning in a mission critical project. Optimism is important for positive thinking to solve problems and for encouragement of project members. On the other hand, pessimism is important for more reliable plans for next actions. Both are important but sometimes they seem to be contradictory. This paper discusses the issue based on our experience in developing a Japanese postal-address recognition system, which had many technical problems. The paper also gives considerations for better management.