This page explains the different kinds of references for purposes of accurately understanding message delivery and partial failure. For orientation it also provides introductory explanations of how these distinctions affect reference equality.
All references are either Sturdy or Live.
The following diagrams illustrate the possible transitions between the states of a Live reference. The most important distinction is that a live reference is either Near , Eventual , or Broken . These Diagrams use David Harel's Statecharts notation, a generalization of state transition diagrams. In statecharts, rounded rectangles represent a state or set of states. So the arrow from Promise to Resolved means that a Promise may become Near , Far , or Broken .