While IRSID is represented as a straightforward, linear, sequential process, in reality it is often more complex and iterative. For example, the view of requirements (I) could be influenced and revised following research into the marketplace and meetings with potential suppliers (R). An initial view on the key performance measures

(SLA, KPIs) would be drafted at the requirements stage (I), but could be reviewed after presentation of proposals by suppliers in the sourcing phase (S). The interaction between the transitioning (I) and the delivery (D) phases is likely to be quite high.