Overview and Meta-Terminology

In general, one can identify the following steps in all definitions or informal descriptions of interactive protocols or protocol classes. 

Static descriptions of the interactive systems. One complete description is called a protocol or scheme. 

An important part is descriptions of the behaviour of individual actors. Here, the word program is used as a generalization of all types of algorithms and functions, and the two most important types of programs will be probabilistic interactive functions and interactive Turing machines. 

The rest of a static description is called the structure description. It contains parameters such as the possible numbers of actors, descriptions of connections, and initial states. 

Concrete embodiments of a scheme or protocol, i.e., something that behaves according to the description. They are called systems.  

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