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Curation and Preservation of CAD Engineering Models in PLM
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Curation and Preservation of CAD Engineering Models in PLM


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A presentation given by Manjula Patel (UKOLN) at the VSMM 2008 Conference (

A presentation given by Manjula Patel (UKOLN) at the VSMM 2008 Conference (

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  • 1. Curation and Preservation of CAD Engineering Models in Product Lifecycle Management Conference on Virtual Systems and MultiMedia dedicated to Digital Heritage 20-25th October 2008 Limassol, Cyprus Manjula Patel, Alexander Ball, Lian Ding UKOLN and IMRC University of Bath, UK This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 UK: Scotland License. To view a copy of this license, visit ; or, (b) send a letter to Creative Commons, 543 Howard Street, 5th Floor, San Francisco, California, 94105, USA. VSMM, 20-25th October 2008, Cyprus
  • 2. Background & Context • Digital Curation: the active management of digital data over its useful lifetime, both for contemporary and future use – Archiving: selection, storage, access over time, including integrity, security and authenticity – Preservation: maintenance of data so it can be accessed and understood through changes in technology • Need for long-term data retention and curation in engineering – Product development and maintenance increasingly collaborative, distributed, global and networked – Product-Service Paradigm – Product Lifecycle Management (PLM) – Legislative and regulatory environment VSMM, 20-25th October 2008, Cyprus
  • 3. Product-Service Paradigm Images courtesy VSMM, 20-25th October 2008, Cyprus
  • 4. Product Lifecycle Management • Efficient capture, representation, organisation, retrieval and reuse of product data over its entire life • Sharing of product information between many geographically distributed organisations • Exchange of information between heterogeneous computer-based systems – CAD/CAE/CAM (Computer Aided Design/Engineering/Manufacture) – ERP/CRM/SCM (Enterprise Resource Planning/ Customer Relationship Management/ Supply Chain Management) • At present, no one single system capable of managing entire product lifecycle VSMM, 20-25th October 2008, Cyprus
  • 5. PLM Information Flows Conceptualisation; Design Organisation; Design; Evaluation; Manufacture & Delivery; Sales & Distribution; Service & Support; Decommission & Disposal Partners Regulators Customers Design team Pre-existing Product 1 information & In service Upgrade In service experience Design team Production Product 2 Design In service Upgrade In service Production VSMM, 20-25th October 2008, Cyprus
  • 6. Digital Curation Lifecycle Model Full lifecycle stages: Description and Representation Information Preservation Planning Community Watch and Participation Curate and Preserve Sequential actions: Conceptualise Create or Receive Appraise and Select Ingest Preservation Action Store Access, Use and Reuse Transform Occasional actions: Dispose © DCC 2008 Reappraise Migrate VSMM, 20-25th October 2008, Cyprus
  • 7. Curatorial issues in PLM (1) • Large variety of data, information and knowledge – Geometric models and databases e.g. test results – Unstructured textual documents e.g. emails, minutes of meetings – Tacit knowledge e.g. design rationale, lessons learnt • Large volumes of data – A single, simple component can be several Megabytes – Complex products (e.g. cars, aircraft) can amount to several Gigabytes or even Terabytes • Global and distributed collaboration – Issues relating to Intellectual Property • Different stages of PLM require different views of the data – Manufacturing engineers need machining features and tolerances – Marketing staff need a final, polished, visualisation of the product VSMM, 20-25th October 2008, Cyprus
  • 8. Curatorial Issues in PLM (2) • Technology obsolescence is exacerbated – CAD software industry is competitive – Move to product-service paradigm • Emulating old software – Difficulties with integration into complex and more modern workflows and systems • Migration – Risk of data loss and subtle design corruption – Rechecking and revalidating costs are substantial • Use of open standards e.g. IGES, STEP – Long timescales make it difficult to keep up with latest capabilities of CAD tools – Level of support for standards is variable between tools • Complex and dynamic environment – Difficult to reliably retrieve and trace provenance information VSMM, 20-25th October 2008, Cyprus
  • 9. CAD Engineering Models • CAD models becoming important in engineering practice – Definitive record of product data – Gradually superseding paper-based specifications – Used directly for communicating design to manufacturers, builders, maintenance crews and regulatory authorities • Problems due to CAD software and formats – Complex dependencies and relationships between file formats, hardware and software – Proliferation of CAD formats; proprietary, closed and subject to frequent change – Interoperability between CAD software is virtually non-existent – Economically unviable to install and run multiple CAD systems VSMM, 20-25th October 2008, Cyprus
  • 10. CAD Model Representations • Traditionally used in Design, Manufacture and Evaluation phases of PLM • Product information stored is still largely based on conventional product representations – Boundary representation (B-rep) – Freeform surface modelling – Feature-based models – Parametric models • Components of a CAD Model – Geometry – Dimensions – Tolerances – Materials – Feature semantics – Model history VSMM, 20-25th October 2008, Cyprus
  • 11. Challenges for CAD Models For CAD models to support information flows in PLM, they need to address: – Protection of commercially sensitive information (Intellectual Property) – Generation of view-point specific representations to support differing processes and users – Rapid sharing of information between geographically distributed applications and users (interoperability, platform and application independence, use of standards, reduced file sizes etc.) – Support for recording feedback from downstream processes – Long-term preservation (recording of metadata, design rationale, open formats, Representation Information, use of standards etc.) VSMM, 20-25th October 2008, Cyprus
  • 12. Proposed Strategy To extend a CAD model from the design stage into all the phases of a product’s lifecycle, we propose the use of: – Lightweight CAD Model Formats (LWFs) – Multilayer annotations – A registry/repository of Representation Information for Engineering Information VSMM, 20-25th October 2008, Cyprus
  • 13. Lightweight CAD Models • Simple formats: do not retain all the richness of a full or native CAD model • Easier to curate and preserve – Simpler and more open specifications – Wider and more affordable software support • Smaller files sizes support distributed exchange – Only contain as much information as a particular recipient needs • Variety of LWFs in current use: – 3D XML, JT Format, PLM XML, PRC, Universal 3D, X3D, XGL/ZGL – Each with properties and characteristics better suited to some purposes than others – Alleviate collaborative exchange, offer customised views, security of IP, application independence, reduced file sizes etc. VSMM, 20-25th October 2008, Cyprus
  • 14. Multilayered Annotation • Need feedback from downstream processes – Being able to augment the geometric model of the product with additional information from different phases of PLM • Annotation allows incorporation of varied information: – Design rationale, context, provenance, etc. – Extra information needed for a certain point of view – Embedding of commercial security levels to restrict access to certain partners or users • “stand-off” (vs. “in-line”) annotation – Stored separately to CAD model; actual model unchanged – Can be selective about which annotations are shared – Same annotation can be applied to derivatives of full CAD model • Use of XML for machine-processing VSMM, 20-25th October 2008, Cyprus
  • 15. LiMMA LiMMA (Lightweight Models with Multilayered Annotations) A framework for representing CAD models using LWFs with additional layers of XML-encoded annotations VSMM, 20-25th October 2008, Cyprus
  • 16. Annotation Environments Annotation interfaces in UGS NX CAD package and PDF VSMM, 20-25th October 2008, Cyprus
  • 17. OAIS Representation Information • A wide range of LWFs with differing characteristics are available • Need format appropriate not only for a particular use and view of the product, but also for long-term retention • Open Archival Information System (OAIS) Reference Model – Preservation and curation environment for all types of data – Developed by CCSDS, published as ISO 14721:2003 – Defines a functional model and an information model – Representation Information is any information required to render, interpret, process and understand data • e.g. Software tools for rendering and interpretation; file format specifications and references; conventions and semantics used • Essential for both curation and contemporary use • A planning tool - Registry/Repository of Representation Information for Engineering (RRoRIfE) VSMM, 20-25th October 2008, Cyprus
  • 18. RRoRIfE • Registry/Repository of Representation Information for Engineering • Holds two XML schemas relating to: – significant properties of CAD file formats – characteristics of conversion software • Facilitates simple preservation planning queries: – Characteristics of file formats and conversion tools – Select a characteristic and see which format supports it – Generate possible migration pathways between two formats – Given a start format and significant characteristics, generate a list of suitable destination formats and conversion pathways VSMM, 20-25th October 2008, Cyprus
  • 19. Further Work & Conclusions • Further Work – Develop an integrated framework – Persistent identification of geometry between native CAD formats and the LWFs derived from them – RRoRIfE: accumulate a corpus of information on significant properties of file formats and characteristics of conversion tools – Non-intrusive and automated capture of information in PLM – Selection and appraisal of product lifecycle data • Conclusions – Digital curation challenges posed by PLM are significant – Several tools and techniques specific to improving the robustness and longevity of CAD file formats • LiMMA (Lightweight Models with Multilayered Annotations) • RRoRIfE (Registry/Repository of Representation Information for Engineering information) VSMM, 20-25th October 2008, Cyprus
  • 20. Questions? Thank you Manjula Patel UKOLN, University of Bath, UK Knowledge and Information Management Through Life Digital Curation Centre (Grand-Challenge) Project Innovative Manufacturing UKOLN Research Centre VSMM, 20-25th October 2008, Cyprus