ISO 10303-108:2005

Industrial automation systems and integration — Product data representation and exchange — Part 108: Integrated application resource: Parameterization and constraints for explicit geometric product models

ISO 10303-108:2005 specifies the resource constructs for the representation of model parameters and constraints in CAD or other kinds of models, together with the mechanisms necessary for associating them with geometric or other elements of transferred models. The use of these capabilities potentially allows certain aspects of the behaviour of a model in its originating system to be conveyed together with the basic model itself. The intention in transferring this additional information is to provide the receiving system with data that will enable it to reconstruct corresponding behavioural characteristics in the model following the transfer. Ideally, this will enable the model to be edited in the receiving system just as as though it had been created there. That would not be possible without the exchange of what is known as design intent information. ISO 10303-108:2005 enables the capture and transfer of an important aspect of design intent. The following are within the scope of ISO 10303-108:2005: parameterization of models through the association of variables with quantities occurring in them, including dimensional values; constraints defining mathematical relationships between variable parameters; constraints on models expressed as descriptive relationships between their constituent elements or attributes of those elements; specialized descriptive constraints corresponding to the geometric constraints commonly used in product shape modelling (e.g., parallelism or tangency between geometric elements); applications of parameterization and constraints to two- and three-dimensional shape models; specialized representations for two-dimensional geometric sketches or profiles; representation of models that are incompletely defined in the sense that certain values in the model may be regarded as not fully constrained. The following are outside the scope of ISO 10303-108:2005: procedural or history-based model representations, expressed in terms of sequences of constructional operations; implicit or procedurally defined constraints, inherent in the operation of constructional operations; solution methods for systems of constraint equations; form features of shape models; behaviour of a system in which a variational model is edited following a transfer; considerations of accuracy in constraint satisfaction. The following notes apply to the excluded capabilities. Procedural or history-based representations are the subject of ISO 10303-55. Methods of solving constraint equations are the responsibility of the application systems involved in the exchange. ISO 10303-108:2005 merely transfers the constraint relationships that need to be solved. Various other parts of ISO 10303 provide representations for different application-oriented views of form features. The information transmitted by the use of ISO 10303-108:2005 is intended to allow implementers to provide 'reasonable' or 'intuitive' behaviour by receiving systems following the transfer of a model in the circumstances mentioned above, but ISO 10303-108:2005 does not prescribe the detailed nature of such behaviour or of its presentation to the system user. Accuracy considerations are essentially the same in the ISO 10303-108:2005 context as those arising generally in the geometric modelling of product shape. Means are provided elsewhere in ISO 10303 for addressing accuracy issues.

Systèmes d'automatisation industrielle et intégration — Représentation et échange de données de produits — Partie 108: Ressources d'application intégrées: Paramétrage et contraintes pour les modèles de produits géométriques explicites

General Information

• Status: Published
• Publication Date: 23-Jan-2005
• ICS: 25.040.40 - Industrial process measurement and control
• Technical Committee: ISO/TC 184/SC 4 - Industrial data
• Drafting Committee: ISO/TC 184/SC 4/WG 12 - STEP product modelling and resources
• Current Stage: 9020 - International Standard under periodical review
• Start Date: 15-Oct-2024
• Completion Date: 15-Oct-2024

Relations

• Corrected By: ISO 10303-108:2005/Cor 2:2014 - Industrial automation systems and integration — Product data representation and exchange — Part 108: Integrated application resource: Parameterization and constraints for explicit geometric product models — Technical Corrigendum 2
• Effective Date: 31-Jul-2021

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 10303-108
First edition
2005-02-01
Industrial automation systems and
integration — Product data
representation and exchange —
Part 108:
Integrated application resource:
Parameterization and constraints for
explicit geometric product models
Systèmes d'automatisation industrielle et intégration — Représentation
et échange de données de produits —
Partie 108: Ressources d'application intégrées: Paramétrage et
contraintes pour les modèles de produits géométriques explicites

Reference number
©
ISO 2005
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
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©  ISO 2005
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
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ii © ISO 2005 – All rights reserved

Contents Page
1 Scope . . . . . . . . . 1
1.1 Parameterizationschema . . . . . . . 2
1.2 Explicitconstraintschema . . . . . . 3
1.3 Variational representation schema . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4 Explicit geometric constraint schema . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.5 Sketchschema . . . . . . . . 4
2 Normativereferences . . . . . . . . 4
3 Terms, definitions and abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1 TermsdefinedinISO10303-1 . . . . . . 5
3.2 TermsdefinedinISO10303-11 . . . . . . 6
3.3 TermsdefinedinISO10303-42 . . . . . . 6
3.4 TermsdefinedinISO10303-43 . . . . . . 6
3.5 TermsdefinedinISO10303-50 . . . . . . 7
3.6 TermsdefinedinISO13584-20 . . . . . . 7
3.7 Othertermsanddefinitions . . . . . . 7
3.8 Abbreviations . . . . . . . . 14
4 Parameterization . . . . . . . . 15
4.1 Introduction . . . . . . . . 15
4.2 Fundamental concepts and assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.2.1 Modelparameters . . . . . . . 16
4.2.2 Parameter binding to an instance attribute . . . . . . . . . . . . . . . . . . . . . 17
4.3 Parameterization type definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.3.1 attributeidentifier . . . . . . . 18
4.4 Parameterization entity definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.4.1 modelparameter . . . . . . . 19
4.4.2 bound modelparameter . . . . . . 20
4.4.3 unbound modelparameter . . . . . . 22
4.4.4 bound parameterenvironment . . . . . . 23
4.4.5 unbound parameterenvironment . . . . . 23
4.4.6 instance attributereference . . . . . . 24
4.4.7 unbound model parametersemantics . . . . . 25
4.4.8 fixed instance attributeset . . . . . . 25
4.4.9 generated finite numericspace . . . . . 26
4.5 Parameterization function definitions . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.5.1 make numericset . . . . . . . 27
4.5.2 validate attributeid . . . . . . 28
5 Explicitconstraint . . . . . . . . 30
5.1 Introduction . . . . . . . . 30
5.2 Fundamental concepts and assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.2.1 Free-form and defined constraints . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.2.2 Simultaneous groups of constraints . . . . . . . . . . . . . . . . . . . . . . . . 32
5.2.3 Use of the current result in the resolution of ambiguities . . . . . . . . . . . . . 32
5.2.4 Directed and undirected constraints . . . . . . . . . . . . . . . . . . . . . . . . 33
5.2.5 Roles of model parameters in free-form constraints . . . . . . . . . . . . . . . . 33
5.2.6 Accuracy of constraint satisfaction . . . . . . . . . . . . . . . . . . . . . . . . . 34
c ISO 2005 — All rights reserved iii

5.3 Explicit constraint type definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.3.1 constraint group member . . . . . . 34
5.4 Explicit constraint entity definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.4.1 explicit constraint . . . . . . . 34
5.4.2 definedconstraint . . . . . . . 35
5.4.3 equal parameterconstraint. . . . . . 36
5.4.4 free formconstraint . . . . . . 37
5.4.5 free formassignment . . . . . . 38
5.4.6 free formrelation . . . . . . . 39
5.4.7 simultaneous constraintgroup . . . . . . 40
6 Variationalrepresentation . . . . . . . 43
6.1 Introduction . . . . . . . . 43
6.2 Fundamental concepts and assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 43
6.3 Variational representation entity definitions . . . . . . . . . . . . . . . . . . . . . . . 45
6.3.1 variational representationitem . . . . . 45
6.3.2 auxiliary geometric representationitem. . . . . 46
6.3.3 variationalrepresentation . . . . . . 46
6.3.4 variational current representationrelationship . . . . 48
6.4 Variational representation function definitions . . . . . . . . . . . . . . . . . . . . . . 49
6.4.1 invalidate vrepitem . . . . . . 49
7 Explicitgeometricconstraint . . . . . . . 52
7.1 Introduction . . . . . . . . 52
7.2 Fundamental concepts and assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 52
7.2.1 Dimensional constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
7.2.2 Semantics of dimensional constraints . . . . . . . . . . . . . . . . . . . . . . . 55
7.2.3 Constraints on procedurally defined model elements . . . . . . . . . . . . . . . 56
7.3 Explicit geometric constraint type definitions . . . . . . . . . . . . . . . . . . . . . . 56
7.3.1 geometric constraintelement . . . . . . 56
7.3.2 point curve or surface constraintelement. . . . 57
7.3.3 curve or surface constraintelement . . . . . 57
7.3.4 linear geometry constraintelement . . . . . 57
7.3.5 radial geometry constraintelement . . . . . 57
7.3.6 axial geometry constraintelement . . . . . 58
7.3.7 swept surface orsolid . . . . . . 59
7.3.8 tangent contacttype . . . . . . 59
7.3.9 parallel offsettype . . . . . . . 59
7.3.10 non negative lengthmeasure . . . . . . 60
7.4 Explicit geometric constraint entity definitions . . . . . . . . . . . . . . . . . . . . . 60
7.4.1 explicit geometricconstraint. . . . . . 60
7.4.2 fixed element geometricconstraint . . . . . 61
7.4.3 parallel geometricconstraint . . . . . . 62
7.4.4 pgc withdimension . . . . . . 63
7.4.5 point distance geometricconstraint . . . . . 64
7.4.6 pdgc withdimension. . . . . . 65
7.4.7 skew line distance geometricconstraint . . . . 65
7.4.8 near pointrelationship . . . . . . 66
7.4.9 curve distance geometricconstraint . . . . . 67
7.4.10 cdgc withdimension . . . . . . 69
7.4.11 surface distance geometricconstraint . . . . . 69
7.4.12 sdgc withdimension . . . . . . 71
ivc ISO 2005 — All rights reserved

7.4.13 radius geometricconstraint . . . . . . 72
7.4.14 rgc with dimension . . . . . . 72
7.4.15 curve length geometricconstraint . . . . . 73
7.4.16 clgc with dimension . . . . . . 74
7.4.17 parallel offset geometricconstraint . . . . . 74
7.4.18 pogc withdimension. . . . . . 76
7.4.19 angle geometricconstraint. . . . . . 77
7.4.20 agc withdimension . . . . . . 78
7.4.21 perpendicular geometricconstraint . . . . . 79
7.4.22 incidence geometricconstraint . . . . . 80
7.4.23 coaxial geometricconstraint . . . . . . 82
7.4.24 tangent geometricconstraint. . . . . . 82
7.4.25 symmetry geometricconstraint . . . . . 84
7.4.26 swept point curve geometricconstraint . . . . . 86
7.4.27 swept curve surface geometricconstraint . . . . 87
7.4.28 curve segmentset . . . . . . . 88
7.4.29 curve smoothness geometricconstraint . . . . . 89
7.4.30 surface patchset . . . . . . . 90
7.4.31 surface smoothness geometricconstraint . . . . 90
8 Sketch . . . . . . . . . 92
8.1 Introduction . . . . . . . . 92
8.2 Fundamental concepts and assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 92
8.3 Sketchtypedefinitions . . . . . . . 93
8.3.1 surface or solidmodel . . . . . . 93
8.3.2 planar curveselect . . . . . . . 94
8.3.3 sketch elementselect . . . . . . 95
8.3.4 sketch basisselect . . . . . . . 95
8.3.5 sketch typeselect . . . . . . . 95
8.3.6 curves orarea . . . . . . . 96
8.4 Sketchentitydefinitions . . . . . . . 96
8.4.1 implicit point onplane . . . . . . 96
8.4.2 implicit planar intersectionpoint . . . . . 98
8.4.3 implicit planar projectionpoint . . . . . 98
8.4.4 implicit planarcurve . . . . . . 99
8.4.5 implicit intersectioncurve . . . . . . 100
8.4.6 implicit projectedcurve . . . . . . 100
8.4.7 implicit model intersectioncurve . . . . . 101
8.4.8 implicit silhouettecurve. . . . . . 101
8.4.9 neutral sketchrepresentation . . . . . . 102
8.4.10 positionedsketch. . . . . . . 103
8.4.11 repositioned neutralsketch . . . . . . 105
8.4.12 implicit explicit positioned sketchrelationship . . . . 106
8.4.13 subsketch . . . . . . . . 107
8.4.14 rigidsubsketch . . . . . . . 108
8.5 Sketchfunctiondefinitions . . . . . . 108
8.5.1 get relative direction2points . . . . . . 108
8.5.2 check curveplanarity . . . . . . 109
8.5.3 get plane of implicitgeometry . . . . . 110
Annex A (normative) Short names of entities . . . . . . . . . . . . . . . . . . . . . . . . . . 113
c ISO 2005 — All rights reserved v

Annex B (normative) Information object registration . . . . . . . . . . . . . . . . . . . . . 115
B.1 Documentidentification . . . . . . . 115
B.2 Schemaidentification . . . . . . . 115
B.2.1 parameterization schemaidentification . . . . . 115
B.2.2 explicit constraint schema identification . . . . . . . . . . . . . . . . . . . . . 115
B.2.3 variational representation schema identification . . . . . . . . . . . . . . . . . 115
B.2.4 explicit geometric constraint schema identification . . . . . . . . . . . . . . . . 116
B.2.5 sketchschemaidentification . . . . . . 116
Annex C (informative) Computer interpretable listings . . . . . . . . . . . . . . . . . . . . . 117
Annex D (informative) EXPRESS-G diagrams . . . . . . . . . . . . . . . . . . . . . . . . . 118
Annex E (informative) Technical discussions . . . . . . . . . . . . . . . . . . . . . . . . . . 137
E.1 Role of parameterization and constraints in procedural and hybrid representations . . . 137
E.2 Justification of representational choices made in this part of ISO 10303 . . . . . . . . 139
E.2.1 Non-binary constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
E.2.2 The modelling of variational representations . . . . . . . . . . . . . . . . . . . 140
E.3 Application-related sketches with specific geometric forms . . . . . . . . . . . . . . . 141
AnnexF(informative) Examples. . . . . . . 142
F.1 Examples of the intended usage of the ISO 10303-108 mechanism for linking param-
eters with attributes of entity instances . . . . . . . . . . . . . . . . . . . . . . . . . . 142
F.1.1 Example
...

INTERNATIONAL ISO
STANDARD 10303-108
First edition
2005-02-01
Industrial automation systems and
integration — Product data
representation and exchange —
Part 108:
Integrated application resource:
Parameterization and constraints for
explicit geometric product models
Systèmes d'automatisation industrielle et intégration — Représentation
et échange de données de produits —
Partie 108: Ressources d'application intégrées: Paramétrage et
contraintes pour les modèles de produits géométriques explicites

Reference number
©
ISO 2005
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

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