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: 9093 - International Standard confirmed
• Completion Date: 05-Dec-2019

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 10303-108:2005(E)
©
ISO 2005

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ISO 10303-108:2005(E)
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ISO 10303-108:2005(E)
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
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ISO 10303-108:2005(E)
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
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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
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ISO 10303-108:2005(E)
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 Example1 . . . . . . . 142
F.1.2 Example2 . . . . . . . 144
F.1.3 Relationship between ISO 10303-108 and ISO 13584-20 . . . . . . . . . . . . . 145
F.2 Example of a two-dimensional sketch . . . . . . . . . . . . . . . . . . . . . . . . . . 147
F.3 Usage of ISO 10303-108 for the representation of incompletely defined models . . . . 148
Bibliography . . . . . . . . . 151
Index . . . . . . . . . . 152
Figures
Figure 1 Schema level diagram of relationships between ISO 10303-108 schemas (inside the
box)andotherresourceschemas . . . . . . xi
Figure 2 Schema level diagram of relationships among ISO 10303-108 schemas . . . . . . . xii
Figure 3 Embedding of a current result representation in a variational representation. 45
Figure D.1 EXPRESS-G diagram of the parameterization schema (1 of 2) . . . . . . . . . . . 119
Figure D.2 EXPRESS-G diagram of the parameterization schema (2 of 2) . . . . . . . . . . . 120
Figure D.3 EXPRESS-G diagram of the explicit constraint schema (1 of 1) . . . . . . . . . . . 121
Figure D.4 EXPRESS-G diagram of the variational representation schema (1 of 1) . . . . . . . 122
Figure D.5 EXPRESS-G diagram of the explicit geometric constraint schema (1 of 10) . . . . 123
Figure D.6 EXPRESS-G diagram of the explicit geometric constraint schema (2 of 10) . . . . 124
Figure D.7 EXPRESS-G diagram of the explicit geometric constraint schema (3 of 10) . . . . 125
Figure D.8 EXPRESS-G diagram of the explicit geometric constraint schema (4 of 10) . . . . 126
Figure D.9 EXPRESS-G diagram of the explicit geometric constraint schema (5 of 10) . . . . 127
Figure D.10 EXPRESS-G diagram of the explicit geometric constraint schema (6 of 10) . . . . 128
Figure D.11 EXPRESS-G diagram of the explicit geometric constraint schema (7 of 10) . . . . 129
Figure D.12 EXPRESS-G diagram of the explicit geometric constraint schema (8 of 10) . . . . 130
Figure D.13 EXPRESS-G diagram of the explicit geometric constraint schema (9 of 10) . . . . 131
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ISO 10303-108:2005(E)
Figure D.14 EXPRESS-G diagram of the explicit geometric constraint schema (10 of 10) . . . 132
Figure D.15 EXPRESS-G diagram of the sketch schema(1of4) . . . . 133
Figure D.16 EXPRESS-G diagram of the sketchschema(2of4) . . . . 134
Figure D.17 EXPRESS-G diagram of the sketch schema(3of4) . . . . 135
Figure D.18 EXPRESS-G diagram of the sketchschema(4of4) . . . . 136
Figure F.1 Key relationships between ISO 10303-108 parameterization schema and ISO
13548 generic expressions schema . . . . . . 146
Figure F.2 A simple sketch composed of line segments and circular arcs . . . . . . . . . . . . 147
Tables
A.1 Shortnamesofentities . . . . . . . 113
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ISO 10303-108:2005(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical com-
mittee has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates
closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical stan-
dardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Stan-
dards adopted by the technical committees are circulated to the member bodies for voting. Publication
as an International Standard requires approval by at least 75% of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this part of ISO 10303 may be the
subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 10303–108 was prepared by Technical Committee ISO/TC184, Industrial automation systems
and integration, Subcommittee SC4, Industrial data.
ISO 10303 consists of a series of parts, under the general title Industrial automation systems and inte-
gration — Product data representation and exchange. The structure of ISO 10303 is described in ISO
10303-1.
Each part of ISO 10303 is a member of one of the following series: description methods, implementa-
tion methods, conformance testing methodology and framework, integrated generic resources, integrated
application resources, application protocols, abstract test suites, application interpreted constructs, and
application modules. This part is a member of the integrated application resources series. The inte-
grated generic resources and the integrated application resources specify a single conceptual product
data model.
A complete list of parts of ISO 10303 is available from the Internet:

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ISO 10303-108:2005(E)
Introduction
ISO 10303 is an International Standard for the computer-interpretable representation of product infor-
mation 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 ex-
change, but also as a basis for implementing and sharing product databases, and as a basis for archiving.
This part of ISO 10303 is a member of the integrated resources series. Major subdivisions of this part of
ISO 10303 are:
— Parameterization schema;
— Explicit constraint schema;
— Variational representation schema;
— Explicit geometric constraint schema;
— Sketch schema.
This part of ISO 10303 provides representations of parameters and constraint relationships for use in
models exchanged using ISO 10303, and specifies mechanisms for the association of such elements with
other elements of the models in which they apply. Parameters and constraints are used in CAD systems
to indicate, respectively, variant and invariant characteristics of a model under editing operations. This
part of ISO 10303 also specifies representations forsketches, two-dimensional geometric configurations,
possibly including parameters and constraints, that are often used by CAD systems as basic elements in
constructional operations.
Models with explicitly represented parameterization and constraints are described asvariational. The
schemas provided are intended in the first instance to supplement the ISO 10303 integrated generic
resources to allow the representation of product shape models enhanced with variational information.
However, the basic mechanisms provided in the first three schemas can be used for representing parame-
terization and constraints in the context of any ISO 10303 model, whether of a product, a plan, a process
or an organization.
Other resource parts of ISO 10303 provide capabilities for the representation and exchange of models
having no associated variational information. That information, if present in the originating system,
affects the behaviour of a model under editing operations there; it forms an important part of what is
sometimes referred to as design intent. The use of this part of ISO 10303 for its capture and transfer
potentially allows the reconstruction of key elements of design intent in a receiving system. The trans-
ferred variational information asserts relationships that already exist in the exchanged model; its purpose
is to initiate processes in the receiving system that will ensure that those relationships are maintained if
the model is modified there. This will assist in the efficient modification of the exchanged model in the
receiving system, through the use of the original designer’s scheme of parameterization and constraints.
Such modification of models transferred using ISO 10303 has proved to be difficult or impossible in the
absence of design intent information.
EXAMPLE It may be desired to optimize the model in the receiving system for structural integrity, or to modify
it to make it cheaper to manufacture.
This part of ISO 10303 is intended to interoperate with other closely related parts, notably ISO 10303-55,
which defines procedural and hybrid representations, specified in terms of the constructional operations
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ISO 10303-108:2005(E)
used in building a model. The primary forms of shape representation used by many modern CAD systems
are of these types. ISO 10303-108 (this document) and ISO 10303-55 between them provide for the
capture of the two major aspects of design intent. Procedural representations are outside the normative
scope of the present document, but annex F provides some discussion of the role of parameterization
and constraints in procedural and hybrid representations, and of the interplay between the explicit and
procedural approaches to shape modelling.
A further aspect of modern CAD systems is their provision of feature-based design methods. This
part of ISO 10303 does not address the topic of features, though it provides essential resources for the
positioning and orientation of features in CAD models.
Three books providing further background on the topics covered by this part of ISO 10303 are given in
the Bibliography [3,4,6].
The contents of the schemas making up this part of ISO 10303 are as follows:
parameterization schema: Mechanisms for associating parameters with variable quantities in an
instantiated EXPRESS model;
explicit constraint schema: Definitions of generic constraint relationships between elements of
an instantiated EXPRESS model;
variational representation schema: Specification of the relationship between parameter and con-
straint information and the non-variational model with which it is associated;
explicit geometric constraint schema: Specialization of the explicit constraint schema for the
representation of commonly used geometric constraints (such as parallelism or tangency) between
explicitly represented elements of geometric models;
sketch schema: Means for the representation of two-dimensional sketches, which may contain
variational elements, for use as basic elements in shape modelling operations.
The relationships of the schemas in this part of ISO 10303 to other schemas that define the integrated
resources of ISO 10303 are illustrated in Figure 1 using the EXPRESS-G notation. EXPRESS-G is
defined in annex D of ISO 10303-11. The internal relationships among ISO 10303-108 schemas are
shown in Figure 2. The schemas occurring in Figure 1 are (with two exceptions that form part of ISO
13584) components of ISO 10303 integrated resources, and they are specified in the following resource
parts:
measure schema ISO 10303-41
product property representation schema ISO 10303-41
support resource schema ISO 10303-41
geometric model schema ISO 10303-42
geometry schema ISO 10303-42
topology schema ISO 10303-42
representation schema ISO 10303-43
mathematical functions schema ISO 10303-50
ISO13584 generic expressions schema ISO 13584-20
ISO13584 expressions schema ISO 13584-20
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ISO 10303-108:2005(E)
mathematical_
functions_schema
parameterization_
schema
ISO13584_generic_
expressions_schema
explicit_constraint_
ISO13584_
schema
expressions_schema
support_resource_
schema
explicit_geometric_
constraint_schema
representation_
schema
variational_represen-
tation_schema
measure_schema
geometry_schema
sketch_schema
product_property_ geometric_model_
topology_schema
representation_schema schema
Figure 1 – Schema level diagram of relationships between ISO 10303-108
schemas (inside the box) and other resource schemas
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ISO 10303-108:2005(E)
parameterization_ explicit_constraint_
schema schema
variational_represen-
tation_schema
explicit_geometric_
sketch_schema
constraint_schema
Figure 2 – Schema level diagram of relationships among ISO 10303-108
schemas
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INTERNATIONAL STANDARD ISO 10303-108:2005(E)
Industrial automation systems and integration —
Product data representation and exchange —
Part 108:
Integrated application resource: Parameterization and
constraints for explicit geometric product models
1 Scope
This part of ISO 10303 specifies the resource constructs for the representation of model parameters
and constraints, 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. This part of ISO 10303 enables the capture and transfer of an important aspect of design
intent.
Clause 4 defines a means for the association of model parameters with individual quantities in the model,
to provide for the editing of dimensional values and other variable attributes. Clause 5 provides for the
modelling of constraint relationships in terms of mathematical relationships among model parameters.
Such constraints are not restricted to the modelling of product shape; they are designed to be applicable
in any situation where it may be useful to capture and transfer mathematically specified relationships.
Clause 5 also defines a class of descriptive (non-mathematical) constraints. Clause 6 defines avariational
representation, containing a model together with all the associated parameters and constraints that poten-
tially facilitate its effective editing following a transfer. Clause 7 defines specialized representations for a
set of explicit geometric constraints applicable specifically to elements of shape models of the boundary
representation and closely related types. These are subtypes of the descriptive constraints specified in
clause 5. Finally, clause 8 provides representations for two-dimensional
...

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 10303-108:2005(E)
©
ISO 2005

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ISO 10303-108:2005(E)

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