There is nothing in this world constant butinconstancy. —SWIFT Project after project designs a set of algorithms and thenplunges into construction of customer-deliverable software on a schedule thatdemands delivery of the first thing built.? In most projects, the first system built is（71） usable. Itmay be too slow, too big, awkward to use, or all three. There is no （72） but to startagain, smarting but smarter, and build a redesigned version in which theseproblems are solved. The discard and （73） may be done in one lump, or it may be done piece-by-piece. But alllarge-system experience shows that it will be done. Where a new system conceptor new technology is used, one has to build a system to throw away, for eventhe best planning is not so omniscient （的） as to get it right the first time. The management question, therefore, is notwhether to build a pilot system and throw it away. You will do that. The onlyquestion is whether to plan in advance to build a （74） , or topromise to deliver the throwaway to customers. Seen this way, the answer ismuch clearer. Delivering that throwaway to customers buys time, but it does soonly at the （75） of agony （极大痛苦）for the user, distraction for the builders while they do theredesign, and a bad reputation for the product that the best redesign will findhard to live down. Hence plan to throw one away; you will,anyhow. （71）