). The standard itself is made of parts. We can group them like this:

	Overview (part 1)
	Express the formal language used to describe the entities (part 11) example of EXPRESS :  ENTITY unit_vector;   a, b : REAL;    c : OPTIONAL REAL;  WHERE    length_1 : a**2 + b**2 + NVL(c, 0.0)**2 = 1.0  END_ENTITY

	Implementation (part 21 for clear text, part 22 for SDAI)
	Testing methodology (part 31)
	Integrated generic resources (part 41, 42, 43, 44, 46) they describe entities common to multiple domain of application: point, line, surface
	Integrated application resources (part 101). Theses resources are already more applicatives and less formal : dimensions for examples
	Application protocol. They use a selection of resources from part 4x and 1xx. They may add extra entities, extra rules. All together they describe a particular use of STEP for a specified domain : automotive industry, architecture etc.. As an example you can have a look at the application protocol for ship structures

Some documentation may be found on the site of the NIST. The STEP on a Page will give you a short graphical view of the STEP structure.

Among the practical things to remember: Nobody transfer general STEP files. A STEP file always follow a definite application protocol. When you explore your capabilities of data transfer with STEP you must explore the different application protocols your system support and those supported by your interlocutor.

	American National Standards Institute
	Welcome to ISO Online
	Among the interesting resources of the NIST site it this repository of parts and process plans in various formats.
	Lists of protocols

PDES

PDES ( Product Data exchange using STEP ) is one of the major contributor to STEP. Developed by the NBS in USA.

PDES, INC The official PDES site