ISO 10303-204:2002

INTERNATIONAL ISO
STANDARD 10303-204
First edition
2002-08-15
Industrial automation systems and
integration — Product data representation
and exchange —
Part 204:
Application protocol: Mechanical design
using boundary representation
Systèmes d'automatisation industrielle et intégration — Représentation
et échange de données de produits —
Partie 204: Protocole d'application: Conception mécanique utilisant une
représentation délimitée
Reference number
©
ISO 2002
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ii © ISO 2002 – All rights reserved

Contents Page
1 Scope . . . . . 1
2 Normativereferences . . . . 3
3 Terms,definitions,andabbreviations . . . . 5
3.1 Terms defined in ISO 10303-1 . . . . 5
3.2 Terms defined in ISO 10303-42 . . . 6
3.3 Terms defined in ISO 10303-44 . . . 6
3.4 Otherdefinitions . . . . 7
3.5 Abbreviations. . . . 8
4 Informationrequirements . . . . 9
4.1 Units of functionality . . . . 11
4.1.1 faceted_B-rep . . . . 12
4.1.2 elementary_B-rep . . . . 13
4.1.3 advanced_B-rep . . . . 14
4.1.4 name_preservation . . . . 16
4.1.5 product_structure. . . . 16
4.1.6 visual_presentation_for_B-rep . . . 17
4.2 Applicationobjects . . . . 18
4.3 Applicationassertions . . . . 34
5 Applicationinterpretedmodel . . . . 38
5.1 Mappingtable . . . . 38
5.2 AIMEXPRESSshortlisting . . . . . 67
6 Conformancerequirements . . . . 93
6.1 Conformanceclass1:B-replevel1(CC1) . . . 94
6.2 Conformanceclass2:B-replevel2(CC2) . . . 94
6.3 Conformanceclass3:B-replevel3(CC3) . . . 95
AnnexA(normative) AIMEXPRESSexpandedlisting . . . . 97
A.1 AIMEXPRESSlisting . . . . 97
AnnexB(normative) AIMshortnames. . . 185
AnnexC(normative) Implementationmethodspecificrequirements . . 192
Annex D (normative) PICS (Protocol Implementation Conformance Statement) proforma . . 193
AnnexE(normative) Informationobjectregistration . . . 195
E.1 Documentidentification . . . . 195
E.2 Schemaidentification. . . . 195
AnnexF(informative) ApplicationActivityModel(AAM) . . . 196
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F.1 AAMdefinitions . . . . 196
F.2 DescriptionofAAMscenario . . . . 200
F.3 Mechanicaldesignrequirementsformodelcontentsandcompleteness . . . 203
F.4 AAMdiagrams . . . . 206
AnnexG(informative) Applicationreferencemodeldiagrams . . 211
AnnexH(informative) AIMEXPRESS-G . . . 224
AnnexJ(informative) Computerinterpretablelisting . . . 243
AnnexK(informative) Technicaldiscussions . . . 244
K.1 Geometricshapedescriptionalternatives. . . 244
K.2 Knownissues . . . . 244
Bibliography . . . . . 246
Index . . . . . 247
Figures
Figure 1 The scope of this part of ISO 10303 in the contexts of CAD models and mechanical
engineeringapplications . . . . ix
Figure2 Dataplanningmodel . . . . x
Figure3 RelationshipsbetweengeometricAICs. . . 40
Figure F.1 Conceptual structure of mechanical design product . . 205
Figure F.2 Industrial manufacturing of mechanical products (node A0) . . 207
Figure F.3 Industrial manufacturing of mechanical products (node A0 expanded) . 208
Figure F.4 Conceptual design (node A3) . . . 209
FigureF.5 Designandevaluation(NodeA4). . . 210
FigureG.1 ARMdiagram(1of12) . . . . 212
FigureG.2 ARMdiagram(2of12) . . . . 213
FigureG.3 ARMdiagram(3of12) . . . . 214
FigureG.4 ARMdiagram(4of12) . . . . 215
Figure G.5 ARM diagram (5 of 12) shell in faceted B-rep . . . . 216
FigureG.6 ARMdiagram(6of12)shellinelementaryoradvanced_B-rep . . 217
FigureG.7 ARMdiagram(7of12)surfaceinadvancedB-rep. . 218
FigureG.8 ARMdiagram(8of12)surfaceinelementaryB-rep. . 219
FigureG.9 ARMdiagram(9of12)curveinadvanced_B-rep . . 220
FigureG.10 ARMdiagram(10of12)curveinelementary_B-rep . . 221
FigureG.11 ARMdiagram(11of12) . . . . 222
FigureG.12 ARMdiagram(12of12)conventionsusedinNIAMdiagrams . . 223
FigureH.1 AIMEXPRESS-GdiagramadvancedB-rep . . . 225
FigureH.2 AIMEXPRESS-Gdiagramadvanced_face. . . 226
Figure H.3 AIM EXPRESS-G diagram surfaces . . . 227
FigureH.4 AIMEXPRESS-Gdiagramcurves . . . 228
FigureH.5 AIMEXPRESS-Gdiagramelementary_surface . . . 229
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FigureH.6 AIMEXPRESS-Gdiagramb_spline_curve . . . 230
FigureH.7 AIMEXPRESS-Gdiagramb_spline_surface . . . 231
FigureH.8 AIMEXPRESS-Gdiagramsurfacecurves . . . 232
FigureH.9 AIMEXPRESS-GdiagramelementaryB-rep . . . . 233
FigureH.10 AIMEXPRESS-GdiagramfaceandcurveinelementaryB-rep . . 234
Figure H.11 AIM EXPRESS-G diagram faceted B-rep . . . 235
Figure H.12 AIM EXPRESS-G diagram product structure . . . . 236
Figure H.13 AIM EXPRESS-G diagram product structure continued . . 237
FigureH.14 AIMEXPRESS-Gdiagramvisualpresentation . . . 238
FigureH.15 AIMEXPRESS-Gdiagramcameramodelandprojection . . 239
FigureH.16 AIMEXPRESS-Gdiagrampointandcurvestyles . . 240
FigureH.17 AIMEXPRESS-Gdiagramsurfacestyles . . . 241
FigureH.18 AIMEXPRESS-Gdiagramvisualpresentationconcluded. . 242
Tables
Table 1 Use of units of functionality within functional levels. . 18
Table2 Mappingtableforadvanced_B-repUoF . . . 41
Table3 Mappingtableforelementary_B-RepUoF . . . 48
Table 4 Mapping table for faceted_B-Rep UoF . . . 52
Table5 Mappingtableforname_preservationUoF . . . 54
Table 6 Mapping table for product_structure UoF . . . 55
Table 7 Mapping table for visual_presentation_for_B-rep UoF . . 59
Table 8 Units of functionality within conformance classes . . 94
Table 9 AIM entities within conformance classes. . . 96
Table B.1 AIM short names of entities . . . . 185
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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 3.
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.
International Standard ISO 10303-204was prepared by Technical Committee ISO TC184/SC4. Industrial
automation systems and integration, Subcommittee SC4 Industrial data.
This International Standard is organised as a series of parts, each published separately. The structure of
this International Standard is decribed in ISO 10303-1.
Each part of this International Standard is a member of one of the following series: decription meth-
ods, implementation methods, conformance testing methodology and framework, integrated generic re-
sources, integrated application resources, application protocols, abstract test suites, application inter-
preted constructs, and application modules. This part is a member of the application protocol series.
A complete list of parts of ISO 10303 is available from Internet:

Annexes A, B, C, D and E form an integral part of this part of ISO 10303. Annexes F, G, H, J and K are
for information only.
vic ISO 2002 — All rights reserved

Introduction
ISO 10303 is an International Standard for the computer-interpretable representation and 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 part of ISO 10303 is a member of the application protocol series.
This Part of ISO 10303 specifies an application protocol (AP) for mechanical design using boundary
representation solid models. A boundary representation solid model provides a complete descripton of
the shape of a solid object by describing precisely the geometry and topology of all its internal and
external boundaries.
This application protocol defines the context, scope, and information requirements for mechanical design
using boundary representation models and specifies the integrated resources necessary to satisfy these
requirements.
Application protocols provide the basis for developing implementations of ISO 10303. Application
protocols provide the basis for developing abstract test suites for the conformance testing of AP imple-
mentations.
Clause 1 defines the scope of the application protocol and summarizes the functionality and data covered
by the AP. An application activity model that is the basis for the definition of the scope is provided in
annex F. The information requirements of the application are specified in clause 4 using terminology
appropriate to the application. A graphical representation of the information requirements, referred to as
the application reference model, is given in annex G.
Resource constructs are interpreted to meet the information requirements. This interpretation produces
the application interpreted model (AIM). This interpretation, given in 5.1, shows the correspondence
between the information requirements and the AIM. The short listing of the AIM specifies the interface
to the integrated resources and is given in 5.2. note that definitions and the EXPRESS provided in
the integrated resources for constructs used in the AIM may include select list items and subtypes not
imported into the AIM. The expanded listing given in Annex A contains the complete EXPRESS of
the AIM without annotation. A graphical representation of the AIM is given in annex H. Additional
requirements for specific implementation methods are given in annex C.
This Part of ISO 10303 contains the definition of conforming boundary representation solid models
and the mechanisms to transfer them via an exchange structure as defined in Part ISO 10303-21. The
exchange of such models, with associated visual presentation information is required during the initial
desgn of a mechanical product and when detailed designs of components are communicated to suppliers
and sub-contractors. In this Part B-reps are characterised by the fact that they can represent models with
only planar surfaces (faceted B-rep), models with only analytical surfaces (elementary B-rep) and models
with sculptured surfaces and curves (advanced B-rep). The application reference environment in which
these B-rep models are used is the generation and exchange of volume-based data in the Computer-aided
Mechanical design process. This application places fundamental requirements on the model exchange
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and the neutral representation of models. The transfer and archiving of B-rep models at different stages
of the design and engineering process requires the following to be maintained:
— the completeness of the models when mapped between application systems;
— the correctness of semantics of the representation;
— the accuracy of the geometric relationships between entity instances which form part of a B-rep
model; in particular all vertices shall lie on the edges using them and all edge_curves shall lie on
each face using this edge as part of the boundary.
Three different classes of implementation are specified in clause 6.
This application protocol was developed as one component of a series of Mechanical Design application
protocols and is complemented by ISO 10303-205 Mechanical design using surface models, see (1).
These Parts share a common application environment and have a similar scope for the representation
of mechanical parts. The significant differences among these Parts of ISO 10303 is in the manner in
which the shape of a mechanical part is represented. In this Part the representation is as a manifold solid
boundary representation model. In ISO 10303-205 the shape of the part is represented by a surface model
in which all surfaces and bounding curves are fully represented. Figure 1 gives a pictorial representation
of the scope of this AP.
NOTE 1 In figure 1 the term scope refers to the intended scope of the information models in this Part of ISO
10303. These information models may be useful as part of an information model for applications shown as ’out of
scope’ in this diagram.
Figure 2 contains the data planning model that gives a high level description of the requirements for this
application protocol, as well as the relationships between the basic data objects.
NOTE 2 A dashed line in figure 2 is used to denote an optional association.
The planning model illustrates that a product may be either a part or an assembly. The shape of a part
or assembly is represented by a shape model which takes the form of one, or more, B-reps. Each B-rep
is either a faceted B-rep, an elementary B-rep, or an advanced B-rep. Names can be associated with
products, parts or shape models. Visual properties may optionally be attached to B-rep models.
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CAD Models6
Other Solid Models
CSG Models
’$
B-rep Models
freeform geometry
B-rep Models
Part 204 Scope
analytic geometry
Faceted B-rep
&%
Surface Models
Wireframe Models
2D Drawings
Mechanical Engineering Applications
-
???????
2d Initial Detail Assemblies FE NC Robotics
Design 3D Design Part Design Analysis Programming
Figure 1 – The scope of this part of ISO 10303 in the contexts of CAD
models and mechanical engineering applications
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PRODUCT
ASSEMBLY PART
SHAPE
NAME
MODEL
VISUAL
B-rep
APPEARANCE
elementary
faceted advanced
B-rep B-rep
B-rep
Figure 2 – Data planning model
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INTERNATIONAL STANDARD
Industrial automation systems and integration —
Product data representation and exchange —
Part 204:
Application protocol:
Mechanical design using boundary representation
1Scope
This part of ISO 10303 specifies the use of the integrated resources necessary for the scope and informa-
tion requirements for the use and exchange of boundary representation solid models in the mechanical
engineering design context.
NOTE The application activity model in annex F provides a graphical representation of the processes and infor-
mation flows that are the basis for the definition of the scope of this part of ISO 10303.
This document describes an application reference environment for the generation and exchange of volume-
based design data in the computer-aided mechanical design process, together with appropriate data mod-
els and a physical file implementation form. The information model supports all geometric and topolog-
ical aspects of a complete description of the shape and size of an object. It was originally developed for
applications in mechanical engineering design using the CAD modelling technique boundary represen-
tation (B-rep) solid modelling and may be appropriate for other application areas using this technique.
The following are within the scope of this Part of ISO 10303:
— Three types of B-rep model that are used to represent shape:
a) faceted B-rep model;
b) B-rep model with elementary surfaces;
c) B-rep model with sculptured surfaces;
— curve and surface geometry;
— curves defined in parameter space (pcurves);
— manifold topology;
— product identification information;
— the association of simple presentation attributes such as line-style, line-width, colour with an entire
B-rep model, or, with geometric or topological elements of a B-rep model;
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— preservation of user-defined names of objects;
— units and measures associated with geometric elements;
— assemblies of parts and sub-assemblies.
The following are outside the scope of this Part of ISO 10303:
— Other types of shape representation:
a) wireframe models;
b) surface models;
c) geometrically trimmed curves and surfaces;
d) constructive solid geometry models;
e) compound B-rep models.
— Geometric and topological data:
a) 2D geometry, other than for the definition of pcurves;
b) self-intersecting geometry;
c) non-manifold topology.
— Dimensioning;
— Tolerances;
— Manufacturing information;
— Advanced presentation features such as multiple views, character fonts and symbols.
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2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute
provisions of this part of ISO 10303. For dated references, subsequent amendments to, or revisions of,
any of these publications do not apply. However, parties to agreements based on this part of ISO 10303
are encouraged to investigate the possibility of applying the most recent editions of the normative docu-
ments indicated below. For undated references, the latest edition of the normative document referred to
applies. Members of ISO and IEC maintain registers of currently valid International Standards.
ISO 10303-1:1994, Industrial automation systems and integration — Product data representation and
exchange— Part 1: Overview and fundamental principles
ISO 10303-11:1994, Industrial automation systems and integration — Product data representation and
exchange— Part 11: Description methods: The EXPRESS language reference manual
ISO 10303-21:1994, Industrial automation systems and integration — Product data representation and
exchange— Part 21: Implementation methods: Clear text encoding of the exchange structure
ISO 10303-22:1998, Industrial automation systems and integration — Product data representation and
exchange— Part 22: Implementation methods: Standard data access interface
ISO 10303-31:1994, Industrial automation systems and integration— Product data representation and
exchange— Part 31: Conformance testing methodology and framework: General concepts
ISO 10303-41:1994, Industrial automation systems and integration — Product data representation and
exchange— Part 41: Integrated generic resources: Fundamentals of product description and support
ISO 10303-42:1994, Industrial automation systems and integration — Product data representation and
exchange— Part 42: Integrated generic resources: Geometric and topological representation
ISO 10303-43:1994, Industrial automation systems and integration — Product data representation and
exchange— Part 43: Integrated generic resources: Representation structures
ISO 10303-44:1994, Industrial automation systems and integration — Product data representation and
exchange— Part 44: Integrated generic resources: Product structure configuration
ISO 10303-46:1994, Industrial automation systems and integration — Product data representation and
exchange— Part 46: Integrated generic resources: Visual presentation.
ISO 10303-511:2001, Industrial automation systems and integration— Product data representation
and exchange— Part 511: Application interpreted construct: Topology bounded surface
ISO 10303-512:1999, Industrial automation systems and integration— Product data representation
and exchange— Part 512: Application interpreted construct: Faceted boundary representation
ISO 10303-513:2000, Industrial automation systems and integration— Product data representation
and exchange— Part 513: Application interpreted construct: Elementary boundary representation
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ISO 10303-514:1999, Industrial automation systems and integration— Product data representation
and exchange— Part 514: Application interpreted construct: Advanced boundary representation
ISO 10303-517:2000, Industrial automation systems and integration— Product data representation
and exchange— Part 517: Application interpreted construct: Mechanical design geometric presentation
1)
ISO 10303-518 , Industrial automation systems and integration — Product data representation and
exchange— Part 518: Application interpreted construct: Mechanical design shaded presentation
ISO/IEC 8824-1:1998, Information technology— Abstract Syntax Notation One (ASN.1): Specification
of basic notation
1)
To be published.
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3 Terms, definitions, and abbreviations
3.1 Terms defined in ISO 10303-1
For the purposes of this part of ISO 10303, the following terms defined in ISO 10303-1 apply.
— abstract test suite;
— application;
— application activity model (AAM);
— application context;
— application interpreted model (AIM);
— application object;
— application protocol (AP);
— application reference model (ARM);
— assembly;
— component;
— conformance class;
— conformance requirement;
— conformance testing;
— context;
— data;
— data exchange;
— implementation method;
— interpretation;
— integrated resource;
— model;
— PICS proforma;
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— presentation;
— product;
— product data;
— resource construct;
— structure;
— unit of functionality (UoF);
3.2 Terms defined in ISO 10303-42
For the purposes of this part of ISO 10303, the following terms defined in ISO 10303-42 apply.
— arcwise connected;
— boundary;
— boundary representation solid model;
— bounds;
— curve;
— euler equations;
— inside;
— interior;
— parameter space;
— surface;
— topological sense.
3.3 Terms defined in ISO 10303-44
For the purposes of this part of ISO 10303, the following terms defined in ISO 10303-44 apply.
— bill_of_material structure;
— component;
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— constituent;
— form, fit and function.
3.4 Other definitions
For the purposes of this part of ISO 10303 the following definitions apply:
3.4.1
advanced B-rep
general boundary representation model which may have any geometric form for the faces and edges. In
particular B-splines may be used to define the face and edge geometry.
3.4.2
computer-aided design
way of designing mechanical and other products utilizing computerized tools.
3.4.3
elementary B-rep
boundary representation model in which all surfaces are planar, cylindrical, conical, spherical or toroidal.
3.4.4
elementary geometry
geometry composed of lines, polylines, conics and elementary_surfaces.
3.4.5
faceted B-rep
simplified boundary representation model with planar faces and implicitly defined edges and vertices.
3.4.6
functional level
indicator used to distinguish geometric complexity of a B-rep model or other representation.
3.4.7
genus
topological property used to classify solids. The genus of a solid is an abstraction for the number of
through holes in the solid.
3.4.8
manifold solid
arcwise connected solid such that, the interior of any infinitessimally small sphere, centred at any point
on the boundary of the solid, is divided into precisely 2 regions, inside and outside the solid respectively.
3.4.9
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normal direction
unit vector perpendicular to a surface and pointing away from the material.
3.4.10
orientation
mathematical sense of curves, loops or edges.
3.4.11
product version
identifier for a variant of a product.
3.5 Abbreviations
For the purposes of this Part of ISO 10303, the following abbreviations apply:
B-rep Boundary representation solid
CAE Computer Aided Engineering
CIM Computer Integrated Manufacturing
CSG Constructive Solid Geometry
FEA Finite Element Analysis
ID Identification
IDEF0 ICAM definition language 0
NIAM Nijssen’s Information Analysis Method
NC Numerical Control
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4 Information requirements
This clause specifies the information required for mechanical design using boundary representation.
The information requirements are specified as a set of units of functionality, application objects, and
application assertions. These assertions pertain to individual application objects and to relationships
between application objects. The information requirements are defined using the terminology of the
subject area of this application protocol.
NOTE 1 A graphical representation of the information requirements is given in annex G.
NOTE 2 The information requirements correspond to those of the activities identified as being within the scope
of this application protocol in annex F.
NOTE 3 The mapping table specified in 5.1 shows how the integrated resources and application interpreted
constructs are used to meet the information requirements of this application protocol.
These requirements apply to system developers developing conforming implementations and to users of
this application protocol to exchange physical files containing B-rep model data. An implementation
claiming to conform to this application protocol shall ensure that the structure and constraints defined by
these information requirements are satisfied when physical files are exchanged.
Functional Levels
The information requirements for mechanical design using boundary representation models are presented
in terms of three distinct levels of functionality. The goal is to classify different implementations into
levels distinguished by the complexity of the shape being represented.
The shape of each part described in this AP is composed of geometry and topology. The topology
structure provides the connectivity and trimming information for the unbounded geometry of the part. In
this Application Protocol the use of a topological entity requires that all associated geometry be defined.
In order to classify different levels of design-shape complexity the criterion used is complexity of surface
geometry. Level 1 has simple surface geometry for each face of the model, and much of the topological
information is implicit. Both level 2 and level 3 provide for a complete explicit representation of the
topology of the part in which all vertices, edges, loops and faces are included. The only distinction
between level 2, and level 3 is in the complexity of the geometric curves and surfaces which are associated
with the topological data. There is no distinction in topology structures between level 3 and level 2.
In this part of ISO 10303 three levels of complexity are defined.
B-rep level 1: Level 1 geometric complexity is for faceted B-rep models with planar surfaces as the
bounding surfaces. Only points and planar polygons which can be implicitly represented by their vertex
points are necessary for this representation.
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At level 1 much of the topological information is implicit. Edge and vertex information is not given and
the shells consist of faces bounded by polygons. The face geometry is implicitly planar. The complete
part shape is represented by the polyhedron.
EXAMPLE 1 box shapes;
EXAMPLE 2 faceted shape approximating a model of more complex shape.
Level 1 models can either be an exact model of a simple part or a simplified model of a more complex
part which is suitable for a selected range of applications such as stereolithography, or finite element
analysis.
Level 1 models can be represented in a more compact form than models from level 2 or level 3: edges
and curves are not required to be explicitly defined, since these are always straight lines; the connecting
points are sufficient for their definition.
EXAMPLE 3 Applications of these models:
a) in rapid prototype manufacturing;
b) for visualization purposes;
c) for collision checks of parts;
d) for kinematic studies;
e) for robot programming and simulations.
B-rep level 2: Level 2 of geometric complexity is for models with elementary surfaces. In this level
the geometry needed to represent the curves and surfaces of objects is elementary analytic geometry.
The surfaces included at this level are the plane, sphere, cylinder, cone, and torus. The curves are lines
and conics. Both curves and surfaces are unbounded, and the bounding information is contained in the
topology data. At this level the complete part shape is represented by an elementary B-rep model.
EXAMPLE 4 Application examples:
— milled parts suitable for 2 D manufacturing;
— turned parts.
EXAMPLE 5 Part examples:
— bolts and screws (excluding the thread detail);
— piston of a simple piston-engine;
— motor housings.
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NOTE 4 For the same part there can exist different model representations, which correspond to different appli-
cation requirements.
NOTE 5 For a part there might exist a representation of level 1 and of level 2.
B-rep level 3: Level 3 of geometric complexity is for B-rep models with advanced surface descriptions.
This level will be used for modelling of parts whose geometric shape is representable with elementary ,
or sculptured surfaces, or swept surfaces with linear or rotational extrusions, or any combination of these.
The generator curves for the extrusion can be analytic or free-form curves. The sculptured surfaces or
free-form curves will be B-spline based. Level 3 includes more general forms of twisted curve and
sculptured surface in addition to all those included in level 2.
EXAMPLE 6 Application examples:
— parts which require 3 to 5 axis NC machining for their manufacturing;
— dies for moulding;
— dies for forming;
— ergonomically formed consumer products.
EXAMPLE 7 Part examples:
— plastic housing of a telephone;
— car surface parts like fenders;
— housing block of a combustion engine.
NOTE 6 Level 3 is a superset of level 2 in the sense that all entities supported at level 2 are also supported at
level 3.
NOTE 7 Level 3 models contain surfaces that may have any shape.
4.1 Units of functionality
This clause specifies the units of functionality for the mechanical design using boundary representation
application protocol. This part of ISO 10303 specifies the following units of functionality:
— faceted_B-rep;
— elementary_B-rep;
— advanced_B-rep;
— name_preservation;
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— product_structure;
— visual_presentation_for_B-rep.
The units of functionality and a description of the functions that each UoF supports are given below. The
application objects included in the UoFs are defined in 4.2.
4.1.1 faceted_B-rep
The faceted B-rep UoF provides the ability to define a boundary representation model all of whose faces
are planar.
The following application objects are used by the faceted_B-rep UoF.
— B-rep;
— Direction;
— Face;
— Faceted_B-rep;
— Geometric_element;
— Global_unit;
— Location;
— Loop;
— Plane;
— Point;
— Poly_loop;
— Shell;
— Surface;
— Topological_element;
— Void.
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4.1.2 elementary_B-rep
The elementary_B-rep UoF provides for the definition of a boundary representation model composed of
shells having topologically bounded elementary surfaces as faces.
The following application objects are used by the elementary_B-rep UoF.
— B-rep;
— Bounded_curve;
— Circle;
— Conic;
— Conical_surface;
— Curve;
— Cylindrical_surface;
— Direction;
— Edge;
— Elementary_B-rep;
— Elementary_surface;
— Ellipse;
— Face;
— Geometric_element;
— Global_unit;
— Hyperbola;
— Line;
— Location;
— Loop;
— Parabola;
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— Plane;
— Point;
— Polyline;
— Shell;
— Spherical_surface;
— Surface;
— Topological_element;
— Toroidal_surface;
— Unbounded_curve;
— Vertex;
— Void.
4.1.3 advanced_B-rep
The advanced_B-rep UoF provides the ability to define a boundary representation model with topologi-
cally bounded surfaces as faces and sculptured geometry.
The following application objects are used by the advanced_B-rep UoF.
— Advanced_B-rep;
— B-rep;
— Bounded_curve;
— Circle;
— Conic;
— Conical_surface;
— Curve;
— Cylindrical_surface;
— Degenerate_toroidal_surface;
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— Direction;
— Edge;
— Elementary_surface;
— Ellipse;
— Face;
— Geometric_element;
— Global_unit;
— Hyperbola;
— Line;
— Location;
— Loop;
— Parabola;
— Pcurve
— Plane;
— Point;
— Polyline;
— Sculptured_surface;
— Shell;
— Spherical_surface;
— Surface;
— Surface_curve;
— Surface_of_extrusion;
— Surface_of_revolution;
— Swept_surface;
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— Topological_element;
— Toroidal_surface;
— Twisted_curve;
— Unbounded_curve;
— Vertex;
— Void.
4.1.4 name_preservation
The name_preservation UoF provides the ability to associate and preserve user defined names with mod-
els or model components. This allows for the preservation of entity names that were defined by a user
by means of a computer-aided application. The user-defined
name of an item is used as an alias to any implementation-dependent identifiers.
The following application objects are used by the name_preservation UoF.
— Name.
4.1.5 product_structure
The product_structure UoF provides the ability to define a product as an assembly of parts or of sub-
assemblies. In this AP each part is defined as a B-rep model. Products are composed of individual parts
and of collections of parts which form so called assemblies. Assemblies may consist of sub-assemblies
and of individual parts. Individual parts are represented by specific geometric shape descriptions as B-
rep models. Assemblies have specific geometric relationships with one another and to individual parts.
This UoF includes the structures for the identification of mechanical parts assemblies and the structure
that links the shape of the parts and assemblies to their identification.
These relationships are given by the following properties:
— a reference from an assembly to another assembly or to a part;
— a geometric relationship, which may be described with a transformation matrix, which allows trans-
lation, rotation, and, if required, mirroring and scaling;
— the assemblies and parts have names which a user may require to be unique within one product
assembly.
The following detailed requirements are met by this UoF:
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— the structural description of assemblies and parts with references to shapes;
— the assembly structure which is independent of the referenced shape of the product;
— the versioning of parts;
— the identification of multiple definitions of parts;
— the specification of the relationship between parts which comprise an assembly;
— the specification of the relationship between a part and its shape representation;
— the specification of the relationship of a part shape to the shape representation of an assembly.
The following application objects are used by the product_structure UoF.
— Assembly;
— Part;
— Product;
— Shape_representation;
— Transformation.
4.1.6 visual_presentation_for_B-rep
The visual_presentation_for_B-rep UoF consists of application objects for the association of elementary
viewing information with geometric or topological components of B-rep models. This enables the user to
specify the visual appearance of points, curves, and surfaces and to assign pre-defined colour, line-style
(dashed, dotted and similar) and line-width to any geometric or topological entity.
The following application objects are used by the visual_presentation_for_B-rep UoF.
— 3D_projection;
— Curve_appearance;
— Light_source;
— Point_appearance;
— Presentation_appearance;
— Screen_image;
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— Surface_appearance.
4.1.7 Relationship of units of functionality to functional levels
NOTE Table 1 shows the relationship between the units of functionality in this AP and the functional levels used
in the definition of conformance classes.
B-rep level 1 B-rep level 2 B-rep level 3
name preservation
product structure
visual presentation for B-rep
faceted B-rep elementary B-rep advanced B-rep
Table 1 – Use of units of functionality within functional levels
4.2 Application objects
This clause specifies the application objects for the mechanical design using boundary representation
application protocol. Each application object is an atomic element which embodies a unique application
concept and contains attributes specifying the data elements of the object. The application objects and
their definitions are given below.
4.2.1 3D_projection
A 3D_projection is a is a type of Presentation_appearance (see 4.2.36) that is a 2-dimensional picture of
a 3-dimensional shape. The picture is the image of a mapping defined by a camera model.
4.2.2 Advanced_B-rep
An Advanced_B-rep is a type of B-rep (see 4.2.4) which may include elementary geometry, sculptured
geometry, and swept geometry.
4.2.3 Assembly
An Assembly is a collection of assemblies or parts which are connected together. It has a name as-
signed, which may describe the functionality, and uses transformations to position its sub-assemblies or
components in space.
The data associated with an Assembly are the following:
— components;
— coordinate_system;
— user_defined_name.
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4.2.3.1 components
The components specifies the constituents of the assembly; these may be individual parts or other assem-
blies.
4.2.3.2 coordinate_system
The coordinate_system specifies the Cartesian coordinate system used to define the geometry of the
Assembly. This is the underlying global rectangular Cartesian coordinate system to which all geometry
refers. A coordinate_system is identified with the context of the shape representation for an Assembly.
4.2.3.3 user_defined_name
The user_defined_name specifies a user-defined identifier for the Assembly. It consists of one or more
words and may describe the functionality of the Assembly.
4.2.4 B-rep
A B-rep is a manifold boundary representation which defines a volume in terms of topology and geome-
try. The geometry is used to describe the shape of the object in terms of surfaces and edge-curves. The
topology bounds the geometry to a finite extent and combines all bounded elements to define a manifold
solid. The material side of the solid is defined by normal vectors to the faces; this normal shall point
away from the material. Each B-rep is either an Advanced_B-rep (see 4.2.2), an Elementary_B-rep (see
4.2.15), or a Faceted_B-rep (see 4.2.19).
The data associated with a B-rep are the following:
— boundary;
— voids.
4.2.4.1 boundary
The boundary specifies the closed Shell (see 4.2.41) that is the outer boundary of the B-rep.
4.2.4.2 voids
The voids specifies a list of Voids (see 4.2.55) inside the B-rep. The voids need not be specified for a
particular B-rep if it has a completely solid interior.
4.2.5 Bounded_curve
A Bounded_curve is a type of Curve (see 4.2.9) with finite extent and identifiable end points. Each
Bounded_curve is either a Polyline (see 4.2.34) or a Twisted_curve (see 4.2.52).
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4.2.6 Circle
A Circle is a type of Conic (see 4.2.7) generated by intersecting a conical surface with a plane perpen-
dicular to the axis of the conical surface.
The data associated with a Circle are the following:
— radius;
— location.
4.2.6.1 radius
The radius specifies the distance of all points on the Circle from the centre.
4.2.6.2 location
The location specifies the centre point of a Circle and the normal direction to the plane of the Circle.
4.2.7 Conic
A Conic is a type of Unbounded_curve (see 4.2.53), it is a planar curve which may be produced as the
intersection of a plane and a conical surface, where the axis of the Conic does not lie in the plane. Each
Conic is either a Circle (se
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