This is a post by Dave Martin on PTC site.
Change is an inevitable fact of the product development process. Requirements change, the market changes, and technology changes; all this results in the need to make engineering changes to our product definition and documentation.
Implementing engineering changes can be expensive and time-consuming when part and assembly models have to be scrapped and started over from scratch. But this doesn’t have to be the case when your models are built with the correct strategy.