STEP and related approaches to Long Term Knowledge Retention Mike Pratt, LMR Systems, UK

1
STEP and related approaches to Long Term
Knowledge RetentionMike Pratt, LMR Systems, UK

• Atlantic Workshop on Long Term Knowledge
  Retention
• Bath, UK
• 12 13 February 2007

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Overview

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

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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).

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Purpose of STEP

• ISO 10303 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.
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STEP neutral file philosophy
STEP
Neutral file method 12 translators for 6
systems (STEP suitable for archiving)
Direct translation 30 translators for 6
systems (what do we archive?)
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ISO 10303-203 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
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PDES Inc. and the LTDR Project

• PDES Inc. is an international industry/government
  consortium, based in North Charleston, SC, USA.
• PDES ? 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).

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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 as design intent, and allows
  reconstruction and modification of the original
  design process, which the first does not.

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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

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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 2006-03-07. 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.

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ISO 10303-59

• 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 10303-59 recently passed its CD ballot and
  will shortly be submitted as a Draft
  International Standard.

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Standards related to ISO 10303-59

• The basis of ISO 10303-59 is a set of guidelines
  for shape model quality drawn up by the
  international consortium SASIG (Strategic
  Automotive product data Standards Industry
  Group).
• ISO 10303-59 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 10303-59 where shape models are concerned,
  and defines standardized procedures for archiving
  and retrieving aerospace information.

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Standards for the capture of engineering design
intent (recently published new STEP parts)

• ISO 10303-55 (Procedural and hybrid
  representation).
• Basic STEP resource for representing construction
  history models.
• ISO 10303-111 (Elements for the procedural
  modelling of solid shapes).
• Feature definitions for use in construction
  history modelling for mechanical CAD.
• ISO 10303-108 (Parameterization and constraints
  for explicit geometric product models).
• ISO 10303-109 (Kinematic and geometric
  constraints for asembly models.
• ISO 10303-112 deals with construction history of
  2D sketches.

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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.

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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
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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.

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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.