Organization of STEP at a glance

STEP is a standard for description of data to be exchanged in the industrial world, managed by ISO(TC184/SC4).

STEP is organized into “PARTS” (parts), which define its general data organization (data format, access mode ..), generic resources (general data definitions, such as Geometry, Topology ..), integrated application resources (sets of generic resources that are common to several application domains), application protocols (which are dedicated to specific application domains), as well as interpreted application constructs (which provide complementary definitions to an application domain). In addition these descriptions, which define data schema itself, in regard of the openness and capability of combinations, recommended practices have been written to help implementors producing best interoperable files.

STEP is very modular in its definition, different application protocols may share many common definitions, so they can interoperate for what they have in common. For a given applicative domain or set of domains, such as 3D CAD, the relevant definitions are taken from such and such parts, which then act as a reference. To support a new domain, additional data and constructs are added.

Each STEP Part is identified by a number; groups of numbers correspond to various kinds of Parts. Here is a list of the most notable STEP Parts in use in 3D mechanical CAD :

  • Part 1 : Overview and fundamental principles
  • Series 1x : Description Methods
  • Part 11 : The EXPRESS language reference manual
  • Series 2x : Implementation method
  • Part 21 : Clear text encoding of the exchange structure
  • …
  • Series 4x : Integrated generic resources
  • Part 41 : Fundamentals of product description and support
  • Part 42 : Geometric and topological representation
  • Part 43 : Representation structures
  • Part 44 : Product structure configuration
  • Part 45 : Materials
  • Part 46 : Visual presentation
  • Part 47 : Shape variation tolerances
  • …
  • Series 1xx : Integrated application resources
  • Part 101 : Draughting
  • Part 109 : Assembly model for products
  • …
  • Series 2xx : Application Protocols (AP)
  • AP 203 : Configuration controlled 3D designs of mechanical parts and assemblies
  • AP 214 : Core data for automotive mechanical design processes
  • AP 242 : Managed Model Based 3D Engineering
  • …
  • Series 5xx : Application Interpreted Constructs (AIC)
  • …
  • Series 1xxx : Application Modules (used for definitions of modular protocols)

The protocols AP203, AP214 and AP242 are seen more in detail in dedicated pages.

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