5 IDEF0 Function Modeling
Abstract IDEF0 is a widely used function modeling method. It is extended from SADTTM (Structured Analysis and Design TechniqueTM) and now is an IEEE standard. IDEF0 is normally used to describe what the system is.The syntax and semantics of IDEF0 are introduced in this chapter. A structured approach for IDEF0 model development is also discussed.
5.1 Introduction to IDEF0
IDEF0 (Integration DEFinition language 0) is a modeling method includ- ing combined graphics and text to obtain understanding, support analysis, provide logic for system adjustment, specify requirements, or support systems level design and integration. IDEF0 is based on SADTTM (Struc- tured Analysis and Design TechniqueTM), developed by Douglas T. Ross and SofTech, Inc. [2]. It includes both a definition of a graphical modeling language (syntax and semantics) and a methodology for developing models. IDEF0 can be used to model various kinds of systems including enter prises, software, hardware, products and so forth. For an AS-IS system, IDEF0 can be used to analyze the system functions and to document its rel- ative mechanisms. For a TO-BE system, IDEF0 can be used for requirements definition and functions specification, and then for an implementation design to meet the requirements. IDEF0 model includes a hierarchical series of diagrams, text, and glossary cross-referenced to each other. Two primary modeling components of this method are functions and data/objects that inter-relate those functions. As a function modeling language, IDEF0 has the following characteristics [1]: • It can graphically describe various kinds of business, manufacturing and other types of enterprise operations to any level of detail. • Its syntax and semantics is simple and coherent to learn, use and under- stand. • It has been used and proven in lots of projects in various kinds of areas. • It is supported by kinds of computer graphics tools and numerous com- mercial products. As well as the IDEF0 graphical and text language, IDEF0 methodology 5.2 Syntax and Semantics of IDEF0 99 offers a set of procedures and techniques for developing and interpreting models, such as for data gathering, diagram construction, review cycles and documentation. IDEF0 provides a systems engineering approach to [1]: • Support systems analysis and design at all levels; • Communicate among analysts, designers, users, managers and so forth; • Provide reference scheme for enterprise analysis, information engineering and resource management.
5.2 Syntax and Semantics of IDEF0 1
IDEF0 defines a series of concepts, symbols and rules for function modeling. It also provides a mechanism to organize models under the same project.
5.2.1 Basic Concepts and Rules of IDEF0
The components of the IDEF0 syntax are boxes, arrows, rules, and diagrams. A box represents a function activity and describes what happens in the function, as shown in Fig. 5.1. Each box should have a name and number inside.
Fig. 5.1. Box and arrows
An arrow represents data or object related to functions. They do not represent flow or sequence as in a process model. As shown in Fig. 5.2, syntax rules for arrows include: • Arrows should be drawn in solid line segments. • Arrows should be drawn vertically or horizontally, not diagonally. • Arrows that bend should be curved using only 90 degree arcs. • Arrow ends should touch the outer boundary of the function box and should not cross into the box. • Arrows should attach at box sides, not at corners.