An IDEF0 model is composed of a hierarchical series of graphic diagrams, and related text, that gradually display increasing levels of detail describing functions and their interfaces within the context of a system. The graphic diagrams define functions and functional relationships via box and arrow syntax and semantics. An IDEF0 model does not mandate that functions be executed in the order in which the functions are shown on the diagrams, and the model does not mandate that all functions must be executed for each project. The structural components and features of a language and the rules that define relationships among them are referred to as the language's syntax. The components of the IDEF0 syntax are boxes and arrows, rules, and diagrams.
Boxes represent functions, defined as activities, processes or transformations.
Arrows represent data or objects related to functions. Rules define how the components are used, and the diagrams provide a format for depicting models both verbally and graphically. The format also provides the basis for model configuration management. A box provides a description of what happens in a designated function. A.2.1.2 Arrows Arrows convey data or objects related to functions to be performed.