ISO 10303-55:2005

INTERNATIONAL ISO
STANDARD 10303-55
First edition
2005-02-01
Industrial automation systems — Product
data representation and exchange —
Part 55:
Integrated generic resource: Procedural
and hybrid representation
Systèmes d'automatisation industrielle — Représentation et échange
de données de produits —
Partie 55: Ressources génériques intégrées — Représentation
procédurale et hybride
Reference number
©
ISO 2005
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ii © ISO 2005 – All rights reserved

Contents Page
1 Scope . . . . . . . . . 1
2 Normative references . . . . . . . . . 2
3 Terms, definitions and abbreviations . . . . . . 2
3.1 Terms defined in ISO 10303-1 . . . . . . 2
3.2 Terms defined in ISO 10303-11 . . . . . . . . 3
3.3 Terms defined in ISO 10303-42 . . . . . . . . 3
3.4 Terms defined in ISO 10303-43 . . . . . . . . 3
3.5 Terms defined in ISO 10303-108 . . . . . . . . 4
3.6 Other terms and definitions . . . . . . 5
3.7 Abbreviations . . . . . . . . . 5
4 Procedural model . . . . . . . . 6
4.1 Introduction . . . . . . . . . . 6
4.2 Fundamental concepts and assumptions . . . . . 6
4.2.1 Procedural models . . . . . . . 7
4.2.2 Hybrid models . . . . . . . . . 8
4.2.3 Explicit selected elements . . . . . . . . 8
4.2.4 Dual models . . . . . . . 9
4.2.5 Representation of constructional operations in procedural models . . 10
4.2.6 Implicit and explicit constraints . . . . . 11
4.2.7 Suppression of constructional operations . . . . 12
4.2.8 Exchange of procedural and hybrid models . . . . 12
4.2.9 Variational cases of procedural and hybrid models . . . . 12
4.3 Procedural model entity definitions . . . . . . 13
4.3.1 explicit procedural representation relationship . . . . . . 13
4.3.2 explicit procedural representation item relationship . . . 14
4.3.3 procedural representation . . . . . . . . 15
4.3.4 procedural representation sequence . . . . . . . 16
4.3.5 user selected elements . . . . . . 17
4.3.6 indirectly selected elements . . . . . . . 18
5 Procedural shape model . . . . . . . . 20
5.1 Introduction . . . . . . . . . . 20
5.2 Fundamental concepts and assumptions . . . . . 20
5.2.1 Procedural shape models . . . . . . 21
5.2.2 Hybrid shape models . . . . . . 22
5.2.3 Explicit selected elements in a shape model . . . . 22
5.2.4 Dual shape representations . . . . . . . . 22
5.2.5 Design rationale for shape models . . . . . 22
5.3 Procedural shape model type definitions . . . . . 23
5.3.1 shape representation item . . . . . . . . 23
5.4 Procedural shape model entity definitions . . . . . . . 23
5.4.1 explicit procedural shape representation relationship. . . 23
5.4.2 explicit procedural geometric representation item relationship . . 24
5.4.3 procedural shape representation . . . . . 25
5.4.4 procedural shape representation sequence . . . . 25
5.4.5 procedural solid representation sequence . . . . 26
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5.4.6 procedural surface representation sequence . . . . 27
5.4.7 procedural wireframe representation sequence . . . . . . 28
5.4.8 user selected shape elements . . . . . . 28
5.4.9 indirectly selected shape elements . . . . . . . 29
Annex A (normative) Short names of entities. . . . . 31
Annex B (normative) Information object registration . . . . 32
B.1 Document identification . . . . . . . 32
B.2 Schema identification . . . . . . . . . 32
B.2.1 procedural model schema identification . . . . . 32
B.2.2 procedural shape model schema identification . . . . . . 32
Annex C (informative) Computer interpretable listings . . . . 33
Annex D (informative) EXPRESS-G diagrams . . . . . 34
Annex E (informative) Examples of the use of this part of ISO 10303 . . . 38
E.1 Example of non-geometric application of procedural modelling . . . . . 38
E.2 Example of intended usage of the procedural shape model schema . . 38
E.3 Example of the use of variational (parameterization and constraint) information with a
procedural model . . . . . . . 40
E.4 Example of the embedding of operation sequences and the recording of design rationale 45
Bibliography . . . . . . . . . . 47
Index . . . . . . . . . . 48
Figures
Figure 1 Schema level diagram of relationships among ISO 10303-55 schemas (inside the
box) and other resource schemas . . . . . . viii
Figure D.1 procedural model schema – EXPRESS-G diagram 1 of 1 . . . 35
Figure D.2 procedural shape model schema – EXPRESS-G diagram 1 of 2 . . . . 36
Figure D.3 procedural shape model schema – EXPRESS-G diagram 2 of 2 . . . . 37
Figure E.1 Relationships between instances of procedural, variational and explicit models for
the cases of (a) no variational model, (b) no procedural model, and (c) all three models. . . 42
Table
A.1 Short names of entities . . . . . . . . . 31
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ivISO 2005 — All rights reserved

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 10303-55 was prepared by Technical Committee ISO/TC 184/SC 4, Industrial automation systems
and integration, Subcommittee SC 4, Industrial data.
ISO 10303 consists of a series of parts, under the general title Industrial automation systems and
integration — 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, implementation
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 generic
resources series. The integrated 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:

Should further parts of ISO 10303 be published, they will follow the same numbering pattern.
cISO 2005 — All rights reserved v

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:
— Procedural model schema;
— Procedural shape model schema.
This part of ISO 10303 provides general mechanisms for the representation of models defined in terms
of the operations used to construct them. The constructional operations themselves are represented by
entity data types defined in other parts of ISO 10303, interpreted as constructors. Procedural models
have the advantage of being easy to edit, simply by changing values of parameters used as arguments of
their constructional operations. Such models are said to embody design intent information, in the sense
that modifications to them conform to the scheme of parameterization imposed by their original creator,
and also comply with any constraints implied by the particular constructional operations used. Thus the
transfer of a procedural model into a receiving system carries with it information as to how the model
will behave when edited following the transfer.
However, procedural models also have the disadvantage of containing (in their purest form) little or no
explicit information about the result of actually performing the sequence of operations. This fact makes
them unsuitable as a basis for the automation of many engineering processes that depend on the use of
explicit geometric information, for example numerically controlled machining or inspection.
Systems for engineering purposes commonly achieve the advantages of both modelling approaches
through the use of a dual representation, comprising a primary representation of the procedural or con-
struction history type together with a secondary explicit representation. Other ISO 10303 resources pro-
vide the elements needed for explicit representions. This part of the standard not only specifies resources
for procedural representations but also provides a dual model capability by enabling the association of
such a model with its corresponding explicit counterpart.
The initial focus of this part of ISO 10303 was to allow the capture and exchange of CAD shape rep-
resentations of the procedural and hybrid types (a hybrid representation is basically procedural but also
contains some explicit elements). However, the capabilities provided also have general applicability
for the transfer of any type of procedurally represented or hybrid model, whether geometric or non-
geometric. In the case of shape models, ISO 10303-42 is the primary resource for the corresponding
explicit representations.
Because procedural representations are inherently parametric, they can be edited by changing the values
of input arguments of constructional procedures. However, this requires that the system operator has
an appropriate level of understanding of the rationale underlying the original constructional method. At
the time of writing, no method is known for capturing design rationale information automatically during
model construction, and provision is therefore made in this part of ISO 10303 for its representation as
descriptive text, assumed to be supplied by the original designer.
It is useful to emphasize the distinction between design intent and design rationale. Design intent is cap-
tured in the schemes of parameterization and constraints imposed upon models during their construction.
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It therefore governs the ways in which a model may be edited. Design rationale, on the other hand, is
concerned with the reasons why a particular configuration or constructional process was adopted, and
therefore with the logic underlying the design intent.
The industry motivation for the exchange of procedural, hybrid and dual representations arises from the
difficulties that have been encountered in the editing of ISO 10303 explicit models in a receiving system,
following a model transfer. If only an explicit model is transferred, as in the past, the design intent
embodied in the procedural component of the dual model in the sending system is lost in the transfer.
The consequences are that received model is incomplete in vital respects, and that editing it is difficult
or i
...