STEP and related approaches to Long Term Knowledge Retention Mike Pratt, LMR Systems, UK Atlantic Workshop on Long Term Knowledge Retention Bath, UK 12 – 13 February 2007

Overview Brief introduction to the STEP standard (ISO 10303) Relevant LTKR activities in the STEP context Summary & acknowledgements.

What is STEP? ISO: the International Organization for Standardization ISO 10303: international standard for the electronic exchange of computer-sensible product data A large standard, with many self-contained but mutually consistent parts, covering a range of different product types and product life- cycle stages informally known as STEP (STandard for the Exchange of Product model data) STEP development committee: ISO TC184 (Automation Systems & Integration) SC4 (Industrial Data).

Purpose of STEP ISO is an International Standard for the computer- interpretable representation of product information and for the exchange of product data. The objective is to provide a neutral mechanism capable of describing products throughout their life cycle. This mechanism is suitable not only for neutral file exchange, but also as a basis for implementing and sharing product databases, and as a basis for archiving. This text is required boilerplate in the Foreword of every part of the STEP standard. Initially, emphasis was on exchange and sharing of data, but there is now increasing focus on archiving.

STEP neutral file philosophy F ED C BA F ED C BA STEP Neutral file method: 12 translators for 6 systems (STEP suitable for archiving) Direct translation: 30 translators for 6 systems (what do we archive?)

ISO : Configuration Controlled 3D Designs of Mechanical Parts and Assemblies Configuration Management Authorization Control(Version/Revision) Effectivity Release Status Security Classification Supplier Geometric Shapes Advanced BREP Solids Faceted BREP Solids Manifold Surfaces with Topology Wireframe with Topology Surfaces and Wireframe without Topology Specifications Surface Finish Material Design Process CAD Filename Product Structure Assemblies Bill of Materials Part Substitute Part Alternate Part This is Edition 1 of AP203 – Edition 2 will add many new capabilities

PDES Inc. and the LTDR Project PDES Inc. is an international industry/government consortium, based in North Charleston, SC, USA. PDES Ξ Product Data Exchange using STEP PDES Inc. is concerned with the implementational and other practical aspects of the use of the STEP standard. One of their primary current projects is in Long Term Data Retention (LTDR).

Important aspects of archived data There is little point in the long-term retention of data that are unreliable or not fit for purpose; STEP and its parent ISO subcommittee are starting to address the problem of assessing data reliability. Much more specifically, in the engineering design context, archived data may take one of two forms: The final result of the design process, or A description of the design process that led to that final result. The second form captures more of what is described asdesign intent, and allows reconstruction and modification of the original design process, which the first does not.

Reliability of archived data The STEP community (ISO TC184/SC4) is addressing this topic on two fronts: Development of ISO 8000, a generic standard for data quality. This work is at an early stage. Attention will be given to issues such as the provenance of the data (did it come from a reliable source?), and also whether it is current (has it been superseded?) Development of Part 59 of STEP, which specifically addresses the quality of CAD data models

ISO 8000 A new project, based in newly created WG13 of ISO TC184/SC4 Statement of intent (November 2006): Establish a coherent definition of the structure of Quality Standards to be produced by SC4, based on the results of the Product Data Quality Strategy meeting held on Formulate NWIs and develop the necessary standards for accreditation of organizations and processes, and the quality criteria for information complying with each of the SC4 standards, all to be published under the ISO 8000 series. There are some political issues, not least a perception in some quarters that the primary focus should be on catalogue data.

ISO This standard concerns the quality of CAD shape models. There are many very specific issues arising here. A bad shape model generated at the design stage can severely impact the effectiveness of downstream engineering processes. The many criteria defined concern such things as whether the elements making up the boundary of the 3D shape model are properly connected, and whether shape elements are appropriately represented for data exchange or archiving. ISO recently passed its CD ballot and will shortly be submitted as a Draft International Standard.

Standards related to ISO The basis of ISO is a set of guidelines for shape model quality drawn up by the international consortium SASIG (Strategic Automotive product data Standards Industry Group). ISO formalizes and quantifies these guidelines. The Association of European Aerospace Industries (in collaboration with Boeing) is also developing a related standard, EN9300 (LOTAR – Long Term Archiving and Retrieval of digital technical product documentation such as 3D, CAD and PDM data). This is intended to be compatible with ISO where shape models are concerned, and defines standardized procedures for archiving and retrieving aerospace information.

Standards for the capture of engineering design intent (recently published new STEP parts) ISO (Procedural and hybrid representation). Basic STEP resource for representing construction history models. ISO (Elements for the procedural modelling of solid shapes). Feature definitions for use in construction history modelling for mechanical CAD. ISO (Parameterization and constraints for explicit geometric product models). ISO (Kinematic and geometric constraints for asembly models. ISO deals with construction history of 2D sketches.

For archiving, is it best to store the explicit detailed final model, or the construction history used to build it? At the 2006 meeting, Doug Cheney of ITI Transcendata suggested the explicit final model should be stored. My personal opinion is that you get a lot more (and possibly avoid some problems) if you store the construction history. The STEP recommendation is to store both. Construction history model is concise, and preserves the design intent which is lost in the explicit model. The explicit model serves as a check on the reconstructed form after a model transfer or extraction from an archive.

Sample part used in recent NIST test of parametric model transfer using new STEP capabilities, and members of its part family The family was generated by making parametric changes to the transferred model in the receiving system

Summary The STEP standard community is addressing the issue of data quality for archiving on two fronts: general aspects quality of CAD models, specifically. Other specialized STEP data quality resources will be developed as the needs are perceived.

Acknowledgments US National Institute of Standards and Technology (NIST), for supporting the authors participation in the work described; Heriot-Watt University, UK, for funding the authors attendance at this workshop.