An act of communication is like jumping across a gap between two buildings. Sometimes the gap is narrow enough to be jumped without anything special needing to be done. But very often, communication fails because the gap, as first encountered, is too wide to jump. In a subset of the difficult cases, something can be done to improve the jumping ability or to narrow the gap. One can sometimes increase the success rate by modifying the string so it can jump further or one can improve the chances by building out from the far side so there is less far to jump.
