During the Iteration, No Changes from External Stakeholders

Iterative and agile methods embrace change, but not chaos. In a sea of constant change, a point of stability is necessary. In IID methods this is achieved with the rule:

Once the requests for an iteration have been chosen and it is underway, no external stakeholders may change the work.

One week into a three-week iteration, the product manager should not come along, and ask, "Can you do this too?" They wait for the next iteration. However, the team itself can reduce the scope of an iteration if the timebox deadline cannot otherwise be met.

scope reduction: primary and secondary iteration goals