ISO 10303-43:2000

Industrial automation systems and integration - Product data representation and exchange - Part 43: Integrated generic resource: Representation structures

Systèmes d'automatisation industrielle et intégration — Représentation et échange de données de produits — Partie 43: Ressources génériques intégrées: Structures de représentation

General Information

• Status: Withdrawn
• Publication Date: 16-Aug-2000
• Withdrawal Date: 16-Aug-2000
• 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: 9599 - Withdrawal of International Standard
• Start Date: 02-Apr-2012
• Completion Date: 13-Dec-2025

Relations

• Revises: ISO 10303-43:1994/Cor 2:2000 - Industrial automation systems and integration - Product data representation and exchange - Part 43: Integrated generic resources: Representation structures - Technical Corrigendum 2
• Effective Date: 15-Apr-2008
• Revises: ISO 10303-43:1994 - Industrial automation systems and integration - Product data representation and exchange - Part 43: Integrated generic resources: Representation structures
• Effective Date: 15-Apr-2008
• Revises: ISO 10303-43:1994/Cor 1:1999 - Industrial automation systems and integration - Product data representation and exchange - Part 43: Integrated generic resources: Representation structures - Technical Corrigendum 1
• Effective Date: 15-Apr-2008

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 10303-43
Second edition
2000-08-15
Industrial automation systems and
integration — Product data representation
and exchange —
Part 43:
Integrated generic resource:
Representation structures
Systèmes d'automatisation industrielle et intégration — Représentation
et échange de données de produits —
Partie 43: Ressources génériques intégrées: Structures de
représentation
Reference number
©
ISO 2000
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ii © ISO 2000 – All rights reserved

Contents Page
1 Scope. 1
2 Normative references. 2
3 Terms and definitions . 2
3.1 Terms defined in ISO 10303-1 . 2
3.2 Terms defined in ISO 10303-41 . 3
3.3 Other terms and definitions . 3
4 Representation . 3
4.1 Introduction . 4
4.2 Fundamental concepts and assumptions. 5
4.2.1 Representation. 5
4.2.2 Context of representation. 5
4.2.3 Elements of representation. 5
4.2.4 Association of representations . 6
4.2.5 Transformation. 7
4.2.6 Uncertainty. 8
4.3 Representation type definitions . 8
4.3.1 compound_item_definition . 8
4.3.2 founded_item_select . 9
4.3.3 list_representation_item. 9
4.3.4 set_representation_item . 9
4.3.5 transformation. 9
4.4 Representation entity definitions. 9
4.4.1 compound_representation_item. 9
4.4.2 definitional_representation . 10
4.4.3 founded_item . 10
4.4.4 functionally_defined_transformation. 11
4.4.5 global_uncertainty_assigned_context . 12
4.4.6 item_defined_transformation. 12
4.4.7 mapped_item. 13
4.4.8 parametric_representation_context . 15
4.4.9 representation. 15
4.4.10 representation_context . 17
4.4.11 representation_item. 18
4.4.12 representation_item_relationship. 19
4.4.13 representation_map . 20
4.4.14 representation_relationship . 20
4.4.15 representation_relationship_with_transformation. 21
4.4.16 uncertainty_assigned_representation . 23
4.4.17 uncertainty_measure_with_unit. 24
4.4.18 value_representation_item . 25
4.5 Representation function definitions. 25
4.5.1 acyclic_mapped_representation. 25
4.5.2 item_in_context. 27
4.5.3 using_items . 28
4.5.4 using_representations. 29
4.5.5 valid_measure_value. 30
Annex A (normative) Short names of entities. 31
Annex B (normative) Information object registration. 32
Annex C (informative) Computer interpretable listings . 33
Annex D (informative) EXPRESS-G diagrams. 34
Bibliography. 38
Index. 39
Figures
Figure 1 – Relationship of the representation_schema to the ISO 10303 integration architecture.vi
Figure 2 – Example of the use of mapped_item and representation_map . 14
Figure 3 – Example of the use of representation_relationship_with_transformation . 22
Figure D.1 – EXPRESS-G diagram of the representation_schema (Page 1 of 3). 35
Figure D.2 – EXPRESS-G diagram of the representation_schema (Page 2 of 3). 36
Figure D.3 – EXPRESS-G diagram of the representation_schema (Page 3 of 3). 37
Tables
Table A.1 – Short names of entities. 31
iv © ISO 2000 – 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 committee 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 standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives,
Part 3.
Draft International Standards 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 10303-43 was prepared by Technical Committee ISO/TC 184, Industrial
automation systems and integration, Subcommittee SC 4, Industrial data.
This second edition of ISO 10303-43 constitutes a technical revision of the first edition
(ISO 10303-43:1994), which is provisionally retained to support continued use and maintenance of
implementations based on the first edition, and to satisfy the normative references of other parts of
ISO 10303. This edition incorporates the corrections published in ISO 10303-43:1994/Cor.1:1999 and
ISO 10303-43:1994/Cor.2:2000.
This International Standard is organized as a series of parts, each published separately. The parts of
ISO 10303 fall into one of the following series: description methods, integrated resources, application
interpreted constructs, application protocols, abstract test suites, implementation methods, and
conformance testing. The series are described in ISO 10303-1.
A complete list of parts of ISO 10303 is available from the Internet:
.
This part of ISO 10303 is a member of the integrated resources series. The integrated resources
specify a single conceptual product data model.
Annexes A and B form a normative part of this part of ISO 10303. Annexes C and D are for
information only.
Introduction
ISO 10303 is an International Standard for the computer-interpretable representation of product
information 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 exchange, but also as a basis for implementing and sharing product databases, and as a
basis for archiving.
This part of ISO 10303 specifies the representation_schema. This schema specifies the resource
constructs that group elements of product data into collections in order to describe aspects of
products, particularly properties of products. The relationships of the schema in this part of ISO 10303
to other schemas that define the integrated resources of this International Standard are illustrated in
Figure 1 using the EXPRESS-G notation. EXPRESS-G is defined in annex D of ISO 10303-11. The
application_context_schema, product_definition_schema, product_property_definition_schema,
and product_property_representation_schema are specified in ISO 10303-41. The schemas
illustrated in Figure 1 are components of the integrated resources.
application_context_schema
product_definition_schema
product_property_
definition_schema
product_property_
representation_schema
representation_schema
Figure 1 – Relationship of the representation_schema to the ISO 10303
integration architecture
This edition incorporates modifications that are upwardly compatible with the previous edition.
Modifications to EXPRESS specifications are upwardly compatible if:
— instances encoded according to ISO 10303-21, and that conform to an ISO 10303 application
protocol based on the previous edition of this part, also conform to a revision of that application
protocol based on this edition;
vi © ISO 2000 – All rights reserved

— interfaces that conform to ISO 10303-22 and to an ISO 10303 application protocol based on the
previous edition of this part, also conform to a revision of that application protocol based on this
edition;
— the mapping tables of ISO 10303 application protocols based on the previous edition of this part
remain valid in a revision of that application protocol based on this edition.
Technical modifications to ISO 10303-43:1994 are categorized as follows: changes to the EXPRESS
declarations, new EXPRESS declarations, and changes to definitions of EXPRESS entity data types.
The following EXPRESS declarations have been modified:
— acyclic_mapped_representation;
— item_in_context;
— representation;
— uncertainty_measure_with_unit;
— using_representations.
The following EXPRESS declarations have been added:
— compound_item_definition;
— compound_representation_item;
— founded_item;
— founded_item_select;
— list_representation_item;
— representation_item_relationship;
— set_representation_item;
— uncertainty_assigned_representation;
— using_items;
— valid_measure_value;
— value_representation_item.
The definitions of the following EXPRESS data types have been modified:
— functionally_defined_transformation;
— global_uncertainty_assigned_context;
— item_defined_transformation;
— mapped_item;
— parametric_representation_context;
— representation_context;
— representation_item;
— representation_map;
— representation_relationship;
— representation_relationship_with_transformation.
In this International Standard the same English language words may be used to refer to an object in
the real world or to a concept, and as the name of an EXPRESS data type that represents this object or
concept. The following typographical convention is used to distinguish between these. If a word or
phrase occurs in the same typeface as narrative text, the referent is the object or concept. If the word
or phrase occurs in a bold typeface, the referent is the EXPRESS data type. Names of EXPRESS
schemas also occur in a bold typeface.
The name of an EXPRESS data type may be used to refer to the data type itself, or to an instance of
the data type. The distinction between these uses is normally clear from the context. If there is a
likelihood of ambiguity, the phrase “entity data type” or “instance(s) of” is included in the text.
Double quotation marks “ ” denote quoted text. Single quotation marks ‘ ’ denote particular text string
values.
Numbers in brackets [n] are references to documents listed in the Bibliography.
Several components of this part of ISO 10303 are available in electronic form. This access is provided
through the specification of Universal Resource Locators (URLs) that identify the location of these
files on the Internet. If there is difficulty accessing these files contact the ISO Central Secretariat, or
contact the ISO TC 184/SC4 Secretariat directly at: [e-mail].
viii © ISO 2000 – All rights reserved

INTERNATIONAL STANDARD ISO 10303-43:2000(E)
Industrial automation systems and integration –
Product data representation and exchange –
Part 43:
Integrated generic resource: Representation structures
1 Scope
This part of ISO 10303 specifies the resource constructs that group elements of product data into
collections in order to describe aspects of products. This part of ISO 10303 is applicable to the
description of properties of products. The following are within the scope of this part of ISO 10303:
— the specification of contexts for representation;
— the specification of elements of representation;
— the association of elements of representation with one or more contexts in which they are
combined to represent a concept;

— the association of elements of representation such that one defines another;
— a structure for relating two representations such that one participates in the definition of the other;
— a structure for relating two representations in which one does not participate in the definition of
the other;
— constraints to prevent the recursive definition of instances of an element of representation;
— the specification of the transformation of one element of representation to another by specifying
the input and output of the transformation;
— the specification of the transformation of one element of representation to another by specifying
the transforming function.
The following are outside the scope of this part of ISO 10303:
— the complete specification of types of representation, types of elements of representation, and
types of representation context;
— the specification of the uses of representation;
— the association of representation with any of its possible uses;
— constraints requiring a directed relationship between representations;
NOTE A directed relationship exists between items A and B if the meaning of the relationship of A to B is
different from the meaning of B to A. A and B are peers in a non-directed relationship. A directed relationship
can be specified in an annotated EXPRESS schema that uses or specializes this schema.
— constraints forbidding cyclic structures of related representations;
— constraints requiring a directed relationship between the contexts in which related representations
exist;
— constraints forbidding cyclic structures of relationships between representation contexts.
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 documents 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/IEC 8824-1:1995, Information technology – Abstract Syntax Notation One (ASN.1): Specification
of basic notation.
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.
1 )
ISO 10303-41:— , Industrial automation systems and integration – Product data representation and
exchange – Part 41: Integrated generic resource: Fundamentals of product description and support.
3 Terms and definitions
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:
— application;
— application protocol;
— assembly;
— data;
— information;
— integrated resource;
— product;
1)
To be published. (Revision of ISO 10303-41:1994)
2 © ISO 2000 – All rights reserved

— product data;
— structure.
3.2 Terms defined in ISO 10303-41
For the purposes of this part of ISO 10303, the following terms defined in ISO 10303-41 apply:
— agreement of common understanding;
— annotated EXPRESS schema.
3.3 Other terms and definitions
For the purposes of this part of ISO 10303, the following terms and definitions apply:
3.3.1
context of representation
the basis through which elements of a representation are related to each other
3.3.2
element of representation
a data element that participates in the description of a representation, either directly or by describing
other elements of representation
3.3.3
founded
the property of an element of representation that results from its association, direct or indirect, with a
context of representation
3.3.4
representation
an organized collection of associated data elements, collected together for one or more specific uses
4 Representation
The following EXPRESS declaration begins the representation_schema and identifies the necessary
external references.
EXPRESS specification:
*)
SCHEMA representation_schema;
REFERENCE FROM basic_attribute_schema -- ISO 10303-41
(get_description_value,
get_id_value);
REFERENCE FROM measure_schema -- ISO 10303-41
(measure_value,
measure_with_unit);
REFERENCE FROM support_resource_schema -- ISO 10303-41
(bag_to_set,
identifier,
label,
text);
(*
NOTE 1 The schemas referenced above can be found in the following parts of ISO 10303:
basic_attribute_schema ISO 10303-41
measure_schema ISO 10303-41
support_resource_schema ISO 10303-41
NOTE 2 See annex D for a graphical presentation of this schema using the EXPRESS-G notation.
NOTE 3 A listing of the complete EXPRESS schema specified in this part of ISO 10303, without comments or
other explanatory text, is available from the Internet – see annex C.
4.1 Introduction
The subjects of the representation_schema are the structures that relate a collection of elements of
product data to a context. These structures are representations. Representations are used to describe
aspects of products. The associations between representations and the aspects of products they
describe are specified in annotated EXPRESS schemas that use or specialize this schema.
Representations can be used to:
— describe a property or a relationship between two properties, in which the properties are
associated with a complete product or with a part of a product;
NOTE 1 The use of representations to collect elements of product data in order to describe the properties of a
product is specified in ISO 10303-41, and can be specified in annotated EXPRESS schemas that use or
specialize the constructs specified in this part of ISO 10303 and in ISO 10303-41.
— describe a picture.
NOTE 2 The use of representations to collect elements of product data in order to describe a picture of a
product is specified in ISO 10303-46 [6], and can be specified in annotated EXPRESS schemas that use or
specialize the constructs specified in this part of ISO 10303 and in ISO 10303-46.
One representation can be part of another representation.
EXAMPLE 1 A collection of lines and points describes the shape of a wall. This representation can be used as
part of the description of the shape of the building, of which the wall is a part.
Each representation has a context and a collection of elements specified in that context
EXAMPLE 2 For the representation of geometric elements, the context is a coordinate space.
A context can be related to other contexts.
EXAMPLE 3 Local coordinate spaces can be defined for each building in a factory complex. These coordinate
spaces can be related to each other, and to the coordinate space of the factory complex itself.
Transformations between representations can be specified.
4 © ISO 2000 – All rights reserved

4.2 Fundamental concepts and assumptions
4.2.1 Representation
The following concepts and assumptions apply to the portions of this schema that deal with
representation.
a) A representation consists of a collection of elements of representation and a context. A
representation corresponds to an instance of the representation entity data type. By structuring
the elements in this way, relationships between elements can be established. Elements of
representation are related if:
1) they are elements in the same representation, or
2) they are elements in different representations that have the same context, or
3) they are elements in different representations that have different contexts, if the contexts are
related.
EXAMPLE 1 Consider two points with coordinate values of (0,0,0) and (1,0,0). It is not possible to calculate
the distance between these points until it is established that they are in the same coordinate space. The
specification of a point by itself does not contain enough data to state which coordinate space it is in and what
other elements also share that coordinate space. In this part of ISO 10303, a point is an example of an element of
representation, and a coordinate space is an example of a context.
b) A representation can be used more than once. A representation is separate from its use.
EXAMPLE 2 Consider a collection of points and lines in a coordinate space. This collection can be used to
describe the shape of a product. The collection can also be used, possibly with some transformation, to describe
a drawing or picture of the product. Neither of these uses is part of the definition of the collection itself.
NOTE Representations can be specialized further in annotated EXPRESS schemas that use or specialize this
schema.
4.2.2 Context of representation
The following assumptions apply to the portions of this schema that deal with the context of
representation.
— A representation has a context. It is the context in which the elements of the representation are
related. The context of a representation corresponds to an instance of the representation_context
entity data type.
— The context of a representation exists only as a basis for the representations that use it. Therefore,
representation contexts are related only if representations using the contexts are related.
NOTE Representation contexts can be specialized further in annotated EXPRESS schemas that use or
specialize this schema.
EXAMPLE Possible specializations include contexts for geometry, topology, finite element modelling and
kinematic modelling.
4.2.3 Elements of representation
The following concepts and assumptions apply to the portions of this schema that deal with elements
of representation.
— Elements of representation participate directly in a representation, or support the definition of
another element of representation, or both.
EXAMPLE 1 A point could be the only element in the representation of the location of a product, or it could
serve as the end point of a line that is the only element in the representation of the edge of a product. In the first
case the point itself is an element in a representation directly. In the second case, the point serves only to
provide definition for the line entity.
EXAMPLE 2 An element of representation that specifies the presentation of a text string could be part of the
description of a drawing. In this case it participates directly in a representation. The same element of
representation could, alternatively, be part of a dimension callout. In this second case the text is part of the
callout, and participates indirectly in the description of the drawing.
NOTE Elements of representation that describe the presentation of text strings are specified in
ISO 10303-46 [6]. Elements of representation that describe dimension callouts are described in
ISO 10303-101 [8].
— Elements of representation can refer to each other, thereby forming graphs of such elements in
which each graph has an identifiable root. The association of a root element with a context
associates all elements in the graph with the context.
EXAMPLE 3 A curve is defined by a number of points. These points are all in the same coordinate space as
the curve by virtue of their reference from the curve.
— Elements of representation are collected into representations and associated with contexts as a
basis for establishing relationships between elements.
— An element of representation corresponds to an instance of the representation_item entity data
type.
— An association of one or more elements of representation with a context corresponds to an
instance of the representation entity data type.
4.2.4 Association of representations
The following concepts and assumptions apply to the portions of this schema that deal with the
association of representations.
— A representation can be related to another representation.
— One representation can be related to another representation such that they both participate in the
association, but one does not define the other. This type of association corresponds to the
representation_relationship entity data type.
— One representation can be related to another representation such that the first is part of the
definition of the second. This type of association corresponds to the mapped_item and
representation_map entity data types.
— Two collections of representation elements can be unrelated in two separate contexts, and yet be
related in a third context, or be related only as they both participate in a relating structure.
EXAMPLE Two collections of points and lines each represent the shape of a part. Each of those shapes exists
in a separate context independent and completely unrelated to the other. A third context can exist for the shape
of an assembly of which these parts are components. In this third context, all of the elements are related, either
through a direct association of those elements with that context, or through an association of the representations
of the parts with the representation of the assembly.
6 © ISO 2000 – All rights reserved

4.2.5 Transformation
The following concepts and assumptions apply to the portions of this schema that deal with
transformations.
a) Elements in different representations can be compared if
1) the representations have the same context, or
2) a transformation is defined that relates the representations to each other.
b) A transformation can be defined as a function f between a domain A and a range B. The function
f:A→B takes each element a in A and maps it to an element b in B, i.e., f(a)=b. The complete
specification of a transformation requires the following:
1) the set of elements a to be transformed;
2) the set of elements b resulting from the transformations;
3) the definition of the context A that is common to the set of elements a;
4) the definition of the context B that is common to the set of elements b;
5) the function f.
The domain A and the range B are instances of the representation_context entity data type. The
elements a and b are instances of the representation_item entity data type. The relationships
between a and A, and between b and B, are instances of the representation entity data type: a is
an element in a representation whose context is A, b is an element in a representation whose
context is B.
c) Two different approaches are used in this part of ISO 10303 to specify transformations.
1) The function f can be specified. This type of transformation corresponds to the functionally_-
defined_transformation entity data type.
EXAMPLE 1 Two representations are related such that one is rotated and skewed with respect to the other.
This transformation can be specified by a matrix.
NOTE 1 The data structures for particular kinds of transformation functions, such as matrices, are not
specified in this part of ISO 10303.
EXAMPLE 2 Points on a map are related to points on the surface of the earth by a function that transforms the
three dimensional surface to a two dimensional picture, and applies a scaling factor.
2) An element a in context A and an element b in context B that are sufficient to derive the
function can be specified. This type of transformation corresponds to the item_defined_-
transformation entity data type, or to the mapping defined by the mapped_item entity data
type.
EXAMPLE 3 A translation between coordinate spaces can be uniquely determined by two instances of
axis2_placement_3d a1 and b1 (one in each coordinate space), such that f takes a1 and transforms it to b1.
NOTE 2 The axis2_placement_3d entity data type is defined in ISO 10303-42 [3,4].
4.2.6 Uncertainty
Numeric values that are measured or calculated can be imprecise. Uncertainty is a measure of the
interval of confidence associated with this imprecision. In this International Standard, uncertainty can
be specified for:
a) multiple representations that share a common context;
b) individual representations;
c) individual elements of representation.
This part of ISO 10303 supports (a) and (b).
NOTE 1 (c) is supported by ISO 10303-45 [5].
NOTE 2 Uncertainty is unrelated to the subject of tolerances or permitted variations. These are supported by
ISO 10303-47 [7].
The following concepts and assumptions apply to the portions of this schema that deal with
uncertainty:
— The uncertainty for numeric values can be specified for all the representations that share a
context. This is specified using the global_uncertainty_assigned_context entity data type.
— The uncertainty for numeric values can be specified for a representation in a given context. This is
specified using the uncertainty_assigned_representation entity data type.
If uncertainties are specified more than once, the following precedence rules shall apply. The
uncertainty specified for an individual element of representation shall have precedence over the
uncertainty specified by any uncertainty_assigned_representation in which the item participates.
The uncertainty specified by an uncertainty_assigned_representation shall have precedence over
the uncertainty specified by any global_uncertainty_assigned_context in which the representation
participates.
NOTE 3 Uncertainty for an individual element of representation is specified by the
qualified_-
representation_item entity data type, defined in ISO 10303-45 [5].
4.3 Representation type definitions
4.3.1 compound_item_definition
A compound_item_definition is a selection between different aggregations of representation_item
instances.
EXPRESS specification:
*)
TYPE compound_item_definition = SELECT
(list_representation_item,
set_representation_item);
END_TYPE;
(*
8 © ISO 2000 – All rights reserved

4.3.2 founded_item_select
A founded_item_select is a selection between a founded_item and a representation_item.
EXPRESS specification:
*)
TYPE founded_item_select = SELECT
(founded_item,
representation_item);
END_TYPE;
(*
4.3.3 list_representation_item
A list_representation_item is an ordered aggregation of representation_item instances.
EXPRESS specification:
*)
TYPE list_representation_item = LIST [1:?] OF representation_item;
END_TYPE;
(*
4.3.4 set_representation_item
A set_representation_item is an unordered aggregation of representation_item instances.
EXPRESS specification:
*)
TYPE set_representation_item = SET [1:?] OF representation_item;
END_TYPE;
(*
4.3.5 transformation
A transformation is a selection between types of transformation function specifications.
EXPRESS specification:
*)
TYPE transformation = SELECT
(item_defined_transformation,
functionally_defined_transformation);
END_TYPE;
(*
4.4 Representation entity definitions
4.4.1 compound_representation_item
A compound_representation_item is a type of representation_item that is defined by an
aggregation of other instances of representation_item. This aggregation is either ordered or
unordered.
NOTE 1 A compound_representation_item supports the description of aspects of product data using
structured collections.
NOTE 2 The meaning and usage of a structured collection of instances of can be
representation_item
specified in an annotated EXPRESS listing that uses or specializes this entity data type.
EXAMPLE In an application protocol in the domain of ship design, hydrostatic properties of the ship hull can
be represented using a tabular structure composed of instances of list_representation_item.
EX PRESS specification:
*)
ENTITY compound_representation_item
SUBTYPE OF (representation_item);
item_element : compound_item_definition;
END_ENTITY;
(*
Attribute definitions:
item_element: the list_representation_item or set_representation_item whose component
instances of representation_item define the compound_representation_item.
4.4.2 definitional_representation
A definitional_representation is a type of representation that has a parametric_representation_-
context.
EXPRESS specification:
*)
ENTITY definitional_representation
SUBTYPE OF (representation);
WHERE
WR1: 'REPRESENTATION_SCHEMA.PARAMETRIC_REPRESENTATION_CONTEXT' IN
TYPEOF (SELF\representation.context_of_items );
END_ENTITY;
(*
Formal propositions:
WR1: The context of the definitional_representation shall be a parametric_representation_-
context.
4.4.3 founded_item
The founded_item entity data type represents part of an element of representation. A founded_item
can be used only as part of the definition of a representation_item, and is founded through the
participation of the representation_item in a representation. Further, any instances of
representation_item that are part of a founded_item are founded through that participation. A
founded_item cannot be an item in a representation.
NOTE 1 This entity data type allows errors in other parts of ISO 10303 to be corrected in an upwardly
compatible manner. Specifically, it is a supertype of the entity data types composite_curve_segment and
surface_patch, defined in ISO 10303-42 [3,4], and view_volume, defined in ISO 10303-46 [6].
10 © ISO 2000 – All rights reserved

NOTE 2 This entity data type is not intended to be instantiated as a complex instance of two or more of its
defined subtypes composite_curve_segment, surface_patch, and view_volume.
NOTE 3 This entity data type is not intended for any other use apart from the correction of the errors in other
parts of ISO 10303 listed in NOTE 1 above.
EXAMPLE A bounded_curve that is the parent curve of a composite_curve_segment is founded as a result
of the composite_curve_segment being a founded_item that is part of a representation_item (a composite_-
curve). This provides the necessary relationship between the bounded_curve and a geometric_-
representation_context.
NOTE 4 The bounded_curve, composite_curve, and geometric_representation context entity types are
defined in ISO 10303-42 [3,4].
EX PRESS specification:
*)
ENTITY founded_item;
END_ENTITY;
(*
Informal propositions:
IP1: Each founded_item shall participate in the definition of a representation_item.
4.4.4 functionally_defined_transformation
The functionally_defined_transformation entity data type represents a transformation that is
defined by an explicit transformation function, the function f between a domain A and range B.
NOTE 1 Let f be the transformation function between domain A and range B. The function f:A→B takes each
element a in A and maps it to an element b in B, i.e., f(a)=b.
NOTE 2 The transformation function can be specified in an annotated EXPRESS schema that uses or
specializes this entity data type, or in an agreement of common understanding between the partners sharing this
information.
NOTE 3 The function f can be specified in specializations of this entity type, or through constraints on the
population and usage of the description attribute.
EXAMPLE 1 An annotated EXPRESS schema could define a
subtype x_y_plane_mirror_transformation
of this entity type; the definition of the subtype would state that the nature of the functionally defined
transformation is to mirror all instances of representation_item in the x-y plane.
EXAMPLE 2 An annotated EXPRESS schema could associate different natural language translation functions
with the values ‘English to French’ and ‘French to English’, where these are populations of the
description
attribute of functionally_defined_transformation.
EX PRESS specification:
*)
ENTITY functionally_defined_transformation;
name    : label;
description : OPTIONAL text;
END_ENTITY;
(*
Attribute definitions:
name: the label by which the functionally_defined_transformation is known.
description: the text that characterizes the functionally_defined_transformation. The value of the
description need not be specified.
4.4.5 global_uncertainty_assigned_context
A global_uncertainty_assigned_context is a representation_context that specifies uncertainty for
the elements of representation that are associated with it. The uncertainty is specified by instances of
uncertainty_measure_with_unit (see 4.4.17), and applies to all elements of representation that are
expressed in the same measure and that are associated with a representation that has this global_-
uncertainty_assigned_context.
NOTE The precedence rules that apply to uncertainties in numeric quantities are specified in 4.2.6.
EXAMPLE An instance of global_uncertainty_assigned_context specifies uncertainty of 0.01m with respect
to lengths. Unless modified by the precedence rules specified in 4.2.6, this uncertainty applies to each length
that occurs in each representation_item associated with a representation that has this global_uncertainty_-
assigned_context.
EXPRESS specification:
*)
ENTITY global_uncertainty_assigned_context
SUBTYPE OF (representation_context);
uncertainty : SET [1:?] OF uncertainty_measure_with_unit;
END_ENTITY;
(*
Attribute definitions:
uncertainty: the instances of uncertainty_measure_with_unit that apply in the representation_-
context.
4.4.6 item_defined_transformation
An item_defined_transformation is a transformation that is defined by two instances of
representation_item in which one instance of representation_item is the result of applying the
transformation function to the other. The transformation function is not explicitly provided, but it is
derived from the relationship between the instances of representation_item.
The transformation function is a function f between a domain A and range B. The function f:A→B
takes each element a in A and maps it to an element b in B, i.e., f(a)=b.
NOTE 1 In special cases, the inverse transformation function g:B→A can also be derived as app
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