The iron triangle of time cost and scope has been updated to the project diamond.
A while ago I was advised to not only bcome familiar with the concepts in the iron triangle (now diamond), but to take them to the project sponsor and key stakeholders and get the dimensions ranked.
The benefit of doing this is twofold;
1. You quickly reveal the misalignment in stakeholer and sponsor priorities.
2. Your team can then get on and make decisions on scope, quality and schedule without having to refer back to the sterring committee so often.
Ranking priorities highlights the issue that money matters to the peson paying (i.e. the sponsor), but not to frontline managers or SMEs who work with your team day to day on articulating requirements. This may be one of the sources for enterprise project over-runs and scope creep.
By clearly and publicly setting the priorities it gets easier to manage people's expectations abut what can and should be one by the project team.
Take a look at how I think my current project diamond dimensions are ranked by the sponsor.This set of priorities does not line up with the key stakehodlers, but here it is out in public and it becomes a much more managable issue.