ISO 10303

From Wikipedia, the free encyclopedia

The official title of ISO 10303 is Industrial automation systems and integration - Product data representation and exchange.

ISO 10303 is known as STEP or the Standard for the Exchange of Product model data. It is an International Standard for the computer-interpretable representation and exchange of industrial product data. The 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, CAM, CAE, PDM/EDM and other CAx systems. STEP is addressing product data from mechanical and electrical design, analysis and manufacturing, with additional information specific to various industries such as automotive, aerospace, building construction, ship, oil & 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 Catalogue management systems: Requirements

1 Structure
2 History
3 Future of STEP
4 External links
5 See also

[edit] Structure

Main article: List of STEP parts

STEP is divided into many parts, grouped into

Environment
- Parts 1x: Description methods: EXPRESS, EXPRESS-X
- Parts 2x: Implementation methods: STEP-File, STEP-XML, SDAI
- Parts 3x: Conformance testing methodology and framework
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. Every parts 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 modelling 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:

PLM-Services within the OMG for AP214
ISO 14649 Data model for computerized numerical controllers for AP238
PLCS-DEXs within OASIS (organization) for AP239

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 build 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 their schematic representation for process plant
AP236 - Furniture product data and project data"
AP239 - Product life cycle support"

[edit] 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.

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

[edit] Future of STEP

Despite the many successes of STEP there is still a question in users 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.

Fundamentally, product model data is different to 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.

An XML data format is being developed for STEP but the STEP architecture requires the information requirements of an Application Protocol to be mapped into the common set of Integrated Resources. This allows all of the protocols to share the same information and is essential if all of the interfaces shown in Fig. 4 are going to share and reuse the same set of data. However, the sharing necessarily divides the original data into multiple entities that are not so easy to understand in XML or any other format. This is disappointing because one of the attractions of XML is that is self-documenting (at least for programmers and domain experts). Therefore, a new level of documentation is required in the STEP data to show how the information requirements have been mapped. The required structures are currently in development and it is anticipated that STEP will have a self-documenting XML format in the very near future [5].

The real issue that stops faster STEP deployment is the commitment of those with the resources necessary to define the standards. The government does not like to pick solutions for industry, and industry does not like to fund the development of solutions that can also be used by their competitors. Consequently, much work only gets funded in situations of clear and desperate need such as when the high cost of manufacturing is causing excessive job losses.

The Internet and the World Wide Web broke through this cycle when "killer" applications made the benefits of the new infrastructure clear and compelling for all users. AP-203 made STEP useful by allowing solid models to be exchanged between design systems. AP-238 will make STEP compelling for some users by allowing them to machine parts more efficiently. However, like the early Internet there will be alternatives that are considered more reliable by other users. The killer application that makes STEP ubiquitous has yet to be identified.

[5] M. Hardwick, "On STEP-NC and the complexities of product data integration", ACM/ASME Transactions on Computing and Information Science in Engineering", Vol.4, No1, March 2004