Definitions

ISO 10303

ISO 10303

ISO 10303 is an ISO standard for the computer-interpretable representation and exchange of industrial product data. Its official title is "Industrial automation systems and integration - Product data representation and exchange", known as "STEP" or "Standard for the Exchange of Product model data".

Overview

The International standard's objective is to provide a mechanism that is capable of describing product data throughout the life cycle of a product, independent from any particular system. The nature of this description makes it suitable not only for neutral file exchange, but also as a basis for implementing and sharing product databases and archiving.

Typically STEP can be used to exchange data between CAD, Computer-aided manufacturing, Computer-aided engineering, Product Data Management/EDM and other CAx systems. STEP is addressing product data from mechanical and electrical design, Geometric dimensioning and tolerancing, analysis and manufacturing, with additional information specific to various industries such as automotive, aerospace, building construction, ship, oil and gas, process plants and others.

STEP is developed and maintained by the ISO technical committee TC 184, Technical Industrial automation systems and integration, sub-committee SC4 Industrial data. Like other ISO and IEC standards STEP is copyright by ISO and is not freely available. Other standards developed and maintained by ISO TC184/SC4 are:

  • ISO 13584 PLIB - Parts Library
  • ISO 15531 MANDATE - Industrial manufacturing management data
  • ISO 15926 Process Plants including Oil and Gas facilities Life-Cycle data
  • ISO 18629 PSL- Process specification language
  • ISO 18876 IIDEAS - Integration of industrial data for exchange, access, and sharing
  • ISO 22745 Open Technical Dictionary
  • ISO 8000 Data Quality

STEP is closely related with PLIB (ISO 13584, IEC 61360).

History

The evolution of STEP can be divided into three release phases. The development of STEP started in 1984 as a successor of IGES, SET and VDA-FS. In 1994/95 ISO published the initial release of STEP as international standards (IS) with the parts 1, 11, 21, 31, 41, 42, 43, 44, 46, 101, AP201, AP203. Today AP203 Configuration controlled 3D design is still one of the most important parts of STEP and supported by many CAD systems for import and export.

In the second phase the capabilities of STEP got widely extended, primarily for the design of products in the aerospace, automotive, electrical, electronic, and other industries. This phase ended in the year 2002 with the second major release, including the STEP parts AP202, 209, AP210, AP212, AP214, AP224, AP225, AP227, AP232. Basic harmonization between the APs especially in the geometric areas was achieved by introducing the Application Interpreted Constructs (AIC, 500 series).

A major problem with the APs of the first and second release is that they are too big, have too much overlap with each other and are not sufficiently harmonized. These deficits lead to the development of the STEP modular architecture (400 and 1000 series). This activity was primarily driven by new AP covering additional life-cycle phases such as early requirement analysis (AP233) and maintenance and repair (AP239), and also new industrial areas (AP221, 236). In addition older APs prepare for a new edition on a modular basis (AP203, 209, 210). This is an ongoing process.

Structure

STEP is divided into many parts, grouped into

  • Environment
  • Integrated data models
    • The Integrated Resources (IR), consisting of
      • Parts 4x and 5x: Integrated generic resources
      • Parts 1xx: Integrated application resources
      • PLIB ISO 13584-20 Parts library: Logical model of expressions
    • Parts 5xx: Application Integrated Constructs (AIC)
    • Parts 1xxx: Application Modules (AM)
  • Top parts
    • Parts 2xx: Application Protocols (AP)
    • Parts 3xx: Abstract Test Suites (ATS) for APs
    • Parts 4xx: Implementation modules for APs

In total STEP consists of several hundred parts and every year new parts are added or new revisions of older parts are released. This makes STEP the biggest standard within ISO. Each part has its own scope and introduction

The APs are the top parts. They cover a particular application and industry domain and hence are most relevant for users of STEP. Every AP defines one or several Conformance Classes, suitable for a particular kind of product or data exchange scenario. To provide a better understanding of the scope, information requirements and usage scenarios an informative application activity model (AAM) is added to every AP, using IDEF0

STEP is primarily defining data models using the EXPRESS modeling language. Application data according to a given data model can be exchanged either by a STEP-File, STEP-XML or via shared database access using SDAI.

Every AP defines a top data models to be used for data exchange, called the Application Integrated Model (AIM) or in the case of a modular AP called Module Integrated Models (MIM). These integrated models are constructed by choosing generic objects defined in lower level data models (4x, 5x, 1xx, 5xx) and adding specializations needed for the particular application domain of the AP. The common generic data models are the basis for interoperability between APs for different kinds of industries and life cycle stages.

In APs with several Conformance Classes the top data model is divided into subsets, one for each Conformance Class. The requirements of a conformant STEP application are:

  • implementation of either a preprocessor or a postprocessor or both,
  • using one of the STEP implementation methods STEP-File, STEP-XML or SDAI for the AIM/MIM data model and
  • supporting one or several conformance classes of an AP.

Originally every APs was required to have a companion Abstract test suite (ATS) (e.g. ATS303 for AP203), providing Test Purposes, Verdict Criteria and Abstract Test Cases together with example STEP-Files. But because the development of an ATS was very expensive and inefficient this requirement was dropped and replaced by the requirements to have an informal validation report and recommended practises how to use it. Today the recommended practises are a primary source for those going to implement STEP.

The Application Reference Models (ARM) is the mediator between the AAM and the AIM/MIM. Originally its purpose was only to document high level application objects and the basic relations between them. IDEF1X diagrams documented the AP of early APs in an informal way. The ARM objects, their attributes and relations are mapped to the AIM so that it is possible to implement an AP. As APs got more and more complex formal methods were needed to document the ARM and so EXPRESS which was originally only developed for the AIM was also used for the ARM. Over time these ARM models got very detailed till to the point that some implementations preferred to use the ARM instead of the formally required AIM/MIM. Today a few APs have ARM based exchange formats standardized outside of ISO TC184/SC4:

There is a bigger overlap between APs because they often need to refer to the same kind of products, product structures, geometry and more. And because APs are developed by different groups of people it was always an issue to ensure interoperability between APs on a higher level. The Application integrated constructs (AIC) solved this problem for common specializations of generic concepts, primarily in the geometric area. To address the problem of harmonizing the ARM models and their mapping to the AIM the STEP modules were introduced. They contain a piece of the ARM, the mapping and a piece of the AIM, called MIM. Modules are built on each other, resulting in an (almost) directed graph with the AP and conformance class modules at the very top. The modular APs are:

  • AP203 - Configuration controlled 3D design , TS and 2nd edition
  • AP209 - Composite and metallic structural analysis and related design , upcoming 2nd edition
  • AP210 - Electronic assembly, interconnect and packaging design , 2nd edition
  • AP221 - Functional data and schematic representation of process plants
  • AP236 - Furniture product data and project data"
  • AP239 - Product life cycle support"

Coverage of STEP Application Protocols (AP)

The STEP APs can be roughly grouped into the three main areas design, manufacturing and life cycle support.

Design APs:

  • Mechanical:
    • Part 201 - Explicit draughting. Simple 2D drawing geometry related to a product. No association, no assembly hierarchy.
    • Part 203: Configuration controlled 3D designs of mechanical parts and assemblies.
    • Part 204 - Mechanical design using boundary representation
    • Part 207 - Sheet metal die planning and design
    • Part 209 - Composite and metallic structural analysis and related design
    • Part 214 - Core data for automotive mechanical design processes
    • Part 235 - Materials information for the design and verification of products
    • Part 236 - Furniture product data and project data
  • Building
    • Part 202 - Associative draughting. 2D/3D drawing with association, but no product structure.
    • Part 225 - Building elements using explicit shape representation
  • Connectivity oriented electric, electronic and piping/ventilation:
    • Part 210 - Electronic assembly, interconnect and packaging design. The most complex and sohisticated STEP AP.
    • Part 212 - Electrotechnical design and installation.
    • Part 227 - Plant spatial configuration
  • Ship:
    • Part 215 - Ship arrangement
    • Part 216 - Ship moulded forms
    • Part 218 - Ship structures
  • Others:
    • Part 232 - Technical data packaging core information and exchange
    • Part 233 - Systems engineering data representation
    • Part 237 - Fluid dynamics

Manufacturing APs:

  • Part 219 - Dimensional inspection information exchange
  • Part 223 - Exchange of design and manufacturing product information for cast parts, currently on CD level
  • Part 224 - Mechanical product definition for process plans using machining features
  • Part 238 - Application interpreted model for computer numeric controllers
  • Part 240 - Process plans for machined products

Life cycle support APs:

  • Part 239 - Product life cycle support
  • Part 221 - Functional data and schematic representation of process plants

The AP 221 model is very similar to the ISO 15926-2 model, whereas AP221 follows the STEP architecture and ISO 15926-2 has a different architecture. They both use ISO-15926-4 as their common reference data library or dictionary of standard instances. A further development of both standards resulted in Gellish English as general product modeling language that is application domain independent and that is proposed as a work item (NWI) for a new standard.

The original intend of STEP was to publish one integrated data-model for all live cycle aspects. But due to the complexity, different groups of developers and different speed in the development processes, the splitting into several APs was needed. But this splitting made it difficult to ensure that APs are interoperable in overlapping areas. Main areas of harmonization are:

  • AP214 and 203 in the area of 3D mechanical design. AP214 took over all of the functionality of the earlier AP203 edition and then extending the capabilities significantly. Now in 2007 the second edition of AP203 takes over bigger parts of AP214 by adding again new functionality.
  • AP201, 202, 212, 214, 221 and now AP203ed2 for technical drawings with extension in AP212 and 221 for schematic functionality
  • AP214, 224 and 238 for machining features.
  • AP203ed2, 210, 214, 224, 238 for Geometric dimensioning and tolerancing

For complex areas it is clear that more than one APs are needed to cover all major aspects:

  • AP212 and 214 for electro-mechanical products such as a car or a transformer
  • AP203/214, 209 and 210 for electro/electronic-mechanical products
  • AP212, 215, 216, 218, 227 for ships
  • AP203/214, 224, 240 and 238 for the complete design and manufacturing process of piece parts.

Future of STEP

Despite the many successes of STEP there is still a question in user's minds about the speed of its development and deployment [5]. Many critics point out correctly that the XML standards for e-commerce are being developed much more quickly. To match with these mappings from STEP data models into XML on the basis of DTD and later XML-Schema were defined.

Another rather new approach is to use the Semantic Web based on the Web Ontology Language for exchanging product information.

Fundamentally, product model data is different from other kinds of e-commerce data such as invoices, receipts, etc. The traditional method for communicating product model information is to make a drawing and the traditional method to communicate an invoice is to make a form. When you make a drawing or 3D model you need to define information with many subtle and complex relationships and this makes the STEP data exchange problem more difficult.

See also

References

External links

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