because good research needs good data
Preserving Computer-Aided Design
Digital Preservation Coalition Report
Alex Ball
DCC/UKOLN, University of Bath
17 October 2013
Outline
Introduction
Preserving for reference
Preserving for rationale
Preserving for reuse
Preservation approaches
My background
2006 2007 2008 2009 2010 2011 2012 2013 DCC SCARPDPC Technology Watch Report
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Preserving
Computer-Aided
Design (CAD)
DPC Technology Watch Report 13-02 April 2013 Alex Ball
CAD is used for . . .
É 2D design drawings
É Floor/site plans
É Archaeological site records
É 3D product models É 3D architectural models É 3D impressions/ reconstructions of buildings É Virtual worlds É 3D animations 10.000cm 10.000cm
Triform dongle end
Alex Ball UKOLN University of Bath Claverton Down BATH Scale 1:1 Sheet 4 / 6 Date: 5 March 2007 G4: + 0.001 / -0.002 G5: + 0.003 / -0.004 G8: +0.001 / -0.0 kim11pre011ab10 QWE: rty uiop
CAD is used for . . .
É 2D design drawings
É Floor/site plans
É Archaeological site records
É 3D product models É 3D architectural models É 3D impressions/ reconstructions of buildings É Virtual worlds É 3D animations c
CAD is used for . . .
É 2D design drawings
É Floor/site plans
É Archaeological site records
É 3D product models É 3D architectural models É 3D impressions/ reconstructions of buildings É Virtual worlds É 3D animations c
CAD is used for . . .
É 2D design drawings
É Floor/site plans
É Archaeological site records
É 3D product models É 3D architectural models É 3D impressions/ reconstructions of buildings É Virtual worlds É 3D animations c
CAD is used for . . .
É 2D design drawings
É Floor/site plans
É Archaeological site records
É 3D product models É 3D architectural models É 3D impressions/ reconstructions of buildings É Virtual worlds É 3D animations c Alexander C. Schreyer
CAD is used for . . .
É 2D design drawings
É Floor/site plans
É Archaeological site records
É 3D product models É 3D architectural models É 3D impressions/ reconstructions of buildings É Virtual worlds É 3D animations c Harrison Eiteljorg, II
CAD is used for . . .
É 2D design drawings
É Floor/site plans
É Archaeological site records
É 3D product models É 3D architectural models É 3D impressions/ reconstructions of buildings É Virtual worlds É 3D animations c
Ruben Smelik, Tim Tutenel, Klaas Jan de Kraker, Rafael Bidarra
CAD is used for . . .
É 2D design drawings
É Floor/site plans
É Archaeological site records
É 3D product models É 3D architectural models É 3D impressions/ reconstructions of buildings É Virtual worlds É 3D animations c
CAD is used for . . .
É 2D design drawings
É Floor/site plans
É Archaeological site records
É 3D product models É 3D architectural models É 3D impressions/ reconstructions of buildings É Virtual worlds É 3D animations É
Reference
ÉRationale
ÉReuse
– Lubell et al. (2008) http://dx.doi.org/10.2218/ijdc.v3i2.58Importance of preserving CAD
É CAD models remain interesting longer than CAD systems
remain usable
É 3D CAD models cannot be satisfactorily represented in any
other way (e.g. printouts, physical models)
CAD outside the CAD system
CAD System CNC/CAM System Finite Element Analysis System Geographic Information System Animation System High Quality . . .Scenarios of reference
É Maintenance engineer: investigating a fault, using model on
tablet.
É Customer: reviewing the look of a design.
É Design collaborator: fitting in with adjacent components.
U3D
DWF(X)
É Manufacturing a part from an old design.
Scenarios of reference
É Maintenance engineer: investigating a fault, using model on
tablet.
É Customer: reviewing the look of a design.
É Design collaborator: fitting in with adjacent components.
U3D
DWF(X)
É Manufacturing a part from an old design.
Scenarios of rationale use
É Uncovering where a design has gone wrong
É First stage in a redesign process
Construction history modelling
1. Insert cylinderl=20r=1.0
Change cylinderl=40r=0.5
2. Insert sprocketr=3.0
3. Fit sprocket to cylinder 4. Group cylinder and sprocket
5. Scale group by 1.75×
Feature-based modelling
Ribs
Formats for preserving rationale
CAD formats
É DXF: DWG Exchange Format
É STEP (ISO 10303)
É Part 21: Clear text encoding of the exchange structure (‘STEP
file’)
É Part 203: Configuration controlled 3D designs of mechanical
parts and assemblies
É Part 214: Core data for automotive mechanical design processes É Part 242: Managed model-based 3D engineering
Non-CAD formats
Parametric modelling
8 cm 28 cm
8 cm 18 cm
Procedural modelling
c
Procedural Inc.
c
Reusing standard parts
c
Preserving reusability
Reuse of parts in assemblies
É Supported by most visualisation and full exchange formats
Parametric modelling
É Supported by full exchange formats
Procedural and generative modelling É ???
Preserve the original CAD model
• Implies preserving software through emulation.
Pros preserves maximum information; easier to guarantee
provenance.
Cons need to preserve expertise in the system; need an
amenable software licence; hard to maintain integration with current systems.
Rolling format migrations
• Migration to newer format versions or new CAD
systems.
Pros models usable by current designers and software.
Cons cost of validating each migration; incremental data
loss/corruption.
Good for models in active development/use, but not for long-term archiving.
Normalisation
• Migration to (a) STEP/IFC (b) a visualisation format.
Pros only two migrations needed, so limited data
loss/corruption; back-up in case a migration goes wrong.
Cons cost of validating each migration.
Validation
• Creating a set of validation properties at the time of
creation, as a benchmark for testing future interpretations of the model.
• Need to choose properties to test that reflect what is
important to preserve.
Pros provides confidence that any errors/corruption will be
caught.
Cons requires access to original CAD system.
Supporting documentation
É Annotations preserving vulnerable semantics
É Standards and conventions used, e.g. US National CAD Standard
É Client’s specification
É Rationale models
É Process models
Recommendations
É Establish why a CAD model will be kept, then target the
required properties for preservation.
É Create tests that can prove whether these properties have
survived.
É Keep native CAD models for as long as they can be read.
É Normalise to STEP and a visualisation standard (or two).
É Don’t forget supporting documentation, especially local
conventions and ‘house style’.
É Campaign for better support for standard formats in CAD
because good research needs good data
Thank you for your attention
DCC Website:http://www.dcc.ac.uk/
Alex Ball:http://alexball.me.uk/
Preserving CAD DPC Technology Watch Report:
