  Tangle machines are topologically inspired diagrammatic models. Their novel
feature is their natural notion of equivalence. Equivalent tangle machines may
differ locally, but globally they are considered to share the same information
content. The goal of tangle machine equivalence is to provide a
context-independent method to select, from among many ways to perform a task,
the `best' way to perform the task. The concept of equivalent tangle machines
is illustrated through examples in which they represent recursive computations,
networks of adiabatic quantum computations, and networks of distributed
information processing.
