Issues are intended for managing changes to requirements in processes that include upfront design. These are primary user requirements, which may be excessive, contradictory, incorrect, incomplete, and duplicates of each other. User requirements must be turned into high-quality formalized requirements.
When changes are made to requirements, the system can ask you to establish a link to the source Issue that caused the changes to the requirement. This practice keeps the reasons for changing requirements from getting tangled, and separates the decision from a particular analyst.
Changing one part of the project documentation breaks the integrity of other parts of the documentation. For example, a change in a requirement must not only be coded, but must also be reflected in the test and operational documentation. With the documentation integrity control mechanism, you substantially reduce the time spent keeping documentation up to date, and you also reduce the risks of human error.