Architecture / Structure

STEP covers a wide scope and is organized in series of separately developed and published documents (the so-called Parts). Every Part is published through an independent ISO document (ISO 10303-xxx, where xxx denotes the Part number). All documents are available in their current editing state, which is subject to fixed ISO rules:

• New Work Item (NWI)
• Working Draft (WD)
• Committee Draft (CD)
• Draft International Standard (DIS)
• Final Draft International Standard (FDIS)
• International Standard (IS)

• The individual STEP documents are subdivided into series:

• Description Methodes (10 series, ISO 10303-1x)
• The data modelling language EXPRESS is the first international standard for the specification of data models. With its object-oriented approach it is possible to implement
• Objects (Entities) with properties (Attributes)
• Inheritance rules
• Integrity conditions (local rules for objects and global rules for overall object characteristics)
• Object classes (Schemas)
• Relationships between object classes (Schema-Interoperability).

• EXPRESS-X is a method to map two EXPRESS data models onto each other. The main application areas are:    

• The computer-interpretable description of the mapping process within Application Protocols
• The mapping of datasets of one model onto datasets of another model
• Implementation methods (20 series, ISO 10303-2x)
• The traditional data exchange with STEP is based on a sequential file format (Step Physical File Format). This is an ASCII-file, which can be imported and thus interpreted on every computer. The data access method SDAI (Standard Data Access Interface) is the basis for data integration, e.g. using databases which are specified through an EXPRESS schema.
• Integrated Resources? Basic models (40/50 series, ISO 10303-4x, -5x)

• The basic models of the Integrated Resources establish the foundation for all further data models within the scope of STEP. They each describe (possibly in more than one EXPRESS schema) the basic elements for the following data classes:    

• Product identification and -configuration
• Geometrical and topological description
• Representation structures
• Product structure and -configuration
• Material
• Visual representation
• Tolerances
• Process structure and -properties
• Mathematical constructs and descriptions
  All other STEP data models are built on these basic models.
  
  In the first stage, these are the Application Resources with universal contents (100 series, ISO 10303-1xx), e.g. for    
• Drawings
• Finite Element Method´
• Kinematics
  
  In a parallel stage, all those application-oriented (partial) models, which are used in various complex applications, are combined (500 series, ISO 10303-5xx). These are the so-called AICs (Application Interpreted Construct) like    
• Various geometrical description methods (ranging from edgebased wireframe- up to CSG models)
• Geometrical tolerances
  
  
• On the top level, there are the Application Protocols (200 series, ISO 10303-2xx). They specify those data models which are the basis for implementations. Every STEP implementation (e.g. a data exchange processor) is the implementation of an Application Protocol. Currently, there are numerous Application Protocols under development. The few, which have up to now reached the status of an International Standard, include:    

• AP203 (Configuration Controlled Design)
• AP212 (Electrotechnical Design and Installation)
• AP214 (Core Data for Automotive Mechanical Design and Processes)
  Detailed information can be retrieved following the links.