1 软件开发管理者出于对利润和成本的考虑，尽量控制软件开发中的 “改变”和“重建”的发生。因为任何一个改变和重建都会增加软件开发的费用

2 然后， 软件开发者又要考虑一个问题：决定哪些改变”和“重建”是必须的哪些又是可以被忽视。从而做到软件系统的质量和投入软件开放成本这2个因素的一个平衡。

Software development managers, with the consideration of profit and cost, try to control the occurance of "changes" and "reconstructions" in software development, because any changes and reconstructions will increase the cost of software development.

Then, software developers have to consider another problem: deciding which "changes" and "reconstructions" are necessary and which can be ignored, to achieve a balance between the quality of the software system and the input cost of marketing this software ("投入软件开放成本"没看懂,属于瞎翻).