:docnumber: ISO 10303-506:2018-11(E)
:partnumber: 506
:edition: 3
:title-intro-en: Industrial automation systems and integration
:title-main-en: Product data representation and exchange
:title-part-en: Application interpreted construct: Draughting elements
:title-intro-fr: Systèmes d'automatisation industrielle et intégration
:title-main-fr: Représentation et échange de données de produits 
:title-part-fr: Construction interprétée d'application: Éléments de traçage
:doctype: international-standard
:docstage: 60
:docsubstage: 60
:copyright-year: 2018
:keywords: STEP, ISO 10303, integrated resource, application interpreted construct, dimensions, draughting.
:technical-committee-number: 184
:subcommittee-number: 4
:workgroup-number: 12
:library-ics: 25.040.40

[abstract]
ISO 10303-506:2018-11 specifies the integrated resource constructs for Draughting elements.

This document specifies the use of ISO 10303 integrated resources satisfying the requirements for providing the combinations of annotation that present dimensions and draughting callouts on a drawing.

.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.

The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see http://www.iso.org/directives[www.iso.org/directives]).

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents[http://www.iso.org/patents]).

Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISO's adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see http://www.iso.org/iso/foreword.html[www.iso.org/iso/foreword.html].

This document was prepared by Technical Committee ISO/TC 184, _Automation systems and integration_, Subcommittee SC 4, _Industrial data._

This third edition cancels and replaces the second edition (ISO 10303-506:2011), which has been technically revised.

A detailed description of the changes is provided in <<AnnexE>>.

A list of all parts in the ISO 10303 series can be found on the http://standards.iso.org/iso/10303/tech/step_titles.htm[ISO website].

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at https://www.iso.org/members.html[www.iso.org/members.html].

[[introduction]]
== 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 retention and archiving.

An application interpreted construct (AIC) provides a logical grouping of interpreted constructs that supports a specific functionality for the usage of product data across multiple application contexts. An interpreted construct is a common interpretation of the integrated resources that supports shared information requirements among application protocols.

This part of ISO 10303 specifies an application interpreted construct for the description of annotation that presents dimensions and draughting callouts on a drawing. This annotation, in the form of text and symbology, provides additional product data that may be needed to fully define the product or interpret the drawing.

[[scope]]
== Scope

This part of ISO 10303 specifies the interpretation of the integrated resources to satisfy requirements for the representation of draughting elements.
					
 The supported draughting elements are annotations that present dimensions and draughting callouts within a draughting application. 

[[inscope]]
The following are within the scope of this part of ISO 10303:


* the structures for representing single or composite dimensions;

* the structures for representing structured or unstructured dimensions;

* the structures for representing draughting callouts that can be directed by means of leaders, projection curves, or dimension curves. 



[[outscope]]
The following are outside the scope of this part of ISO 10303:


* annotation that is not used in the presentation a dimension or draughting callout.



[bibliography]
== Normative references

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.


[[defns]]
== Terms, definitions and abbreviated terms

[[termsdefns]]
=== Terms and definitions

[[sec_3.1.1]]
==== Terms defined in ISO 5459

For the purposes of this document, the following terms defined in ISO 5459 apply:

* [[term-datum]]datum.



[[sec_3.1.2]]
==== Terms defined in ISO 10209-1

For the purposes of this document, the following terms defined in ISO 10209-1 apply:

* [[term-drawing]]drawing.



[[sec_3.1.3]]
==== Terms defined in ISO 10303-1

For the purposes of this document, the following terms defined in ISO 10303-1 apply:

* [[term-application interpreted model]]application interpreted model;

* [[term-integrated resource]]integrated resource.

* [[term-application]]application;

* [[term-application context]]application context;

* [[term-application interpreted construct]]application interpreted construct;

* [[term-application protocol]]application protocol;

* [[term-implementation method]]implementation method;

* [[term-interpretation]]interpretation;

* [[term-product data]]product data.



[[sec_3.1.4]]
==== Terms defined in ISO 10303-46

For the purposes of this document, the following terms defined in ISO 10303-46 apply:

* [[term-annotation]]annotation.



[[sec_3.1.5]]
==== Terms defined in ISO 10303-101

For the purposes of this document, the following terms defined in ISO 10303-101 apply:

* [[term-callout]]callout;

* [[term-draughting]]draughting.



[[sec_3.1.6]]
==== Other terms and definitions

For the purposes of this document, the following terms and definitions apply:

[[sec_3.1.6.1]]
===== [[term-dimension value]]dimension value

representation of the numerical value of a dimension that describes the magnitude of the dimension

[[abbrv]]
=== Abbreviated terms

For the purposes of this document, the following abbreviated terms apply:

URL:: uniform resource locator
AIC:: Application Interpreted Construct
AP:: Application Protocol

[[schema4]]
== EXPRESS short listing

[[gen]]
== General

 This application interpreted construct provides a consistent set of entities for the description of annotation that presents dimensions and draughting callouts on a drawing. This annotation, in the form of text and symbology, provides additional product data that may be needed to fully define the product or interpret the drawing. This clause defines the information requirements to which implementations shall conform using the EXPRESS language as defined in ISO 10303-11. The following EXPRESS declaration begins the *aic_draughting_elements* schema that uses elements from the integrated resources and contains the types, entity specializations, and functions that are specific to this part of ISO 10303.

Short names of entities defined in this schema are described in Annex A. Unambiguous identification of this schema is defined in Annex B.

[.underline]#EXPRESS specification:#



[source]
--
*)
[[aic_draughting_elements]]
SCHEMA aic_draughting_elements;
--

[[interfaces]]


[source]
--
USE FROM ../../../../data/resources/draughting_element_schema/draughting_element_schema.xml#draughting_element_schema[draughting_element_schema]   -- ISO 10303-101
  (../../../../data/resources/draughting_element_schema/draughting_element_schema.xml#draughting_element_schema.dimension_curve[dimension_curve],
  ../../../../data/resources/draughting_element_schema/draughting_element_schema.xml#draughting_element_schema.dimension_curve_directed_callout[dimension_curve_directed_callout],
  ../../../../data/resources/draughting_element_schema/draughting_element_schema.xml#draughting_element_schema.dimension_curve_terminator[dimension_curve_terminator],
  ../../../../data/resources/draughting_element_schema/draughting_element_schema.xml#draughting_element_schema.draughting_callout[draughting_callout],
  ../../../../data/resources/draughting_element_schema/draughting_element_schema.xml#draughting_element_schema.draughting_callout_relationship[draughting_callout_relationship],
  ../../../../data/resources/draughting_element_schema/draughting_element_schema.xml#draughting_element_schema.leader_curve[leader_curve],
  ../../../../data/resources/draughting_element_schema/draughting_element_schema.xml#draughting_element_schema.leader_directed_callout[leader_directed_callout],
  ../../../../data/resources/draughting_element_schema/draughting_element_schema.xml#draughting_element_schema.leader_terminator[leader_terminator],
  ../../../../data/resources/draughting_element_schema/draughting_element_schema.xml#draughting_element_schema.projection_curve[projection_curve],
  ../../../../data/resources/draughting_element_schema/draughting_element_schema.xml#draughting_element_schema.projection_directed_callout[projection_directed_callout]);

USE FROM ../../../../data/resources/presentation_definition_schema/presentation_definition_schema.xml#presentation_definition_schema[presentation_definition_schema]   -- ISO 10303-46
  (../../../../data/resources/presentation_definition_schema/presentation_definition_schema.xml#presentation_definition_schema.annotation_text_occurrence[annotation_text_occurrence]);
(*
--



NOTE: The schemas referenced above are specified in the following parts:

[quote]
_____
draughting_element_schema:: ISO 10303-101
presentation_definition_schema:: ISO 10303-46
_____



NOTE: See <<AnnexD>> for a graphical representation of this schema.



NOTE: There may be subtypes and items of select lists that appear in the integrated resources that are not imported into the AIC. Constructs are eliminated from the subtype tree or select list through the use of the implicit interface rules of ISO 10303-11. References to eliminated constructs are outside the scope of the AIC. In some cases, all items of the select list are eliminated. Because AICs are intended to be implemented in the context of an application protocol, the items of the select list will be defined by the scope of the application protocol

[[funcon]]
== Fundamental concepts and assumptions

[[entities]]
== aic_draughting_elements entity definitions

[[aic_draughting_elements.angular_dimension]]
==== angular_dimension


An *angular_dimension* is a type of
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.dimension_curve_directed_callout[dimension_curve_directed_callout]
directed by a dimension curve that presents a value of angular distance measure.


NOTE: Figure 1 illustrates three angular dimensions used to depict information about angular distance measures. The figure also illustrates a radius dimension.


[[figure1]]
.Angular and radius dimensions
image::angular_and_radius_dimensions.gif[Angular and radius dimensions]



[.underline]#EXPRESS specification:#



[source]
--
express_ref:[angular_dimension]
--

[[aic_draughting_elements.curve_dimension]]
==== curve_dimension


A *curve_dimension* is a type of
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.dimension_curve_directed_callout[dimension_curve_directed_callout]
directed by a dimension curve that presents a value of distance between two elements, measured along a curved path, 
or the length of a curved element.


NOTE: Figure 2 illustrates two curve dimensions. The dimension with a value of '36.91' depicts the distance between two elements along a path defined by a third element of geometry or annotation. The dimension with a value of '76.64' depicts the length of a curve, measured along the entire path of the curve.


[[figure2]]
.Curve dimension
image::curve_dimension.gif[Curve dimension]



[.underline]#EXPRESS specification:#



[source]
--
express_ref:[curve_dimension]
--

[[aic_draughting_elements.datum_feature_callout]]
==== datum_feature_callout


A *datum_feature_callout* is a type of
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.draughting_callout[draughting_callout]
that presents a datum. 
It shall contain an alphanumeric designation to be used as identification of the datum.


NOTE: Figure 3 illustrates the dimensioning and annotation of specific features of a product. The top view illustrates the specification of Datums 'E' and 'F' and the specification of a diameter dimension with an associated geometrical tolerance. The middle view of the same figure illustrates a specification of Datum 'D'.



[.underline]#EXPRESS specification:#



[source]
--
express_ref:[datum_feature_callout]
--

[[aic_draughting_elements.datum_target_callout]]
==== datum_target_callout


A *datum_target_callout* is a type of
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.draughting_callout[draughting_callout]
that presents a datum target. 
It shall contain an alphanumeric designation and, where applicable, a specification of the diametrical size of the target area.


NOTE: The bottom view in Figure 3 illustrates three datum target points and their associated datum target symbols.


[[figure3]]
.Draughting callouts
image::draughting_callouts.gif[Draughting callouts]



[.underline]#EXPRESS specification:#



[source]
--
express_ref:[datum_target_callout]
--

[[aic_draughting_elements.diameter_dimension]]
==== diameter_dimension


A *diameter_dimension* is a type of
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.dimension_curve_directed_callout[dimension_curve_directed_callout]
directed by a dimension curve that presents a value of the diametrical size of a circular element.


NOTE: Figure 4 illustrates three diameter dimensions. Projection lines can be used to clarify the extent of the dimension.


[[figure4]]
.Diameter dimension
image::diameter_dimension.gif[Diameter dimension]



[.underline]#EXPRESS specification:#



[source]
--
express_ref:[diameter_dimension]
--

[[aic_draughting_elements.dimension_callout_component_relationship]]
==== dimension_callout_component_relationship


A *dimension_callout_component_relationship* is a type of
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.draughting_callout_relationship[draughting_callout_relationship]
that identifies the association between a 
<<aic_draughting_elements.structured_dimension_callout>> 
and a 
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.draughting_callout[draughting_callout] 
that participates in its definition either as prefix information or suffix information.
A dimension prefix specification is information used in interpreting the dimension or its applicability 
and is physically located before the dimension value as the dimension is read. 
A dimension suffix specification is physically located after the dimension value as the dimension is read and 
either contains information used in interpreting the dimension or its applicability or contains additional information 
that is used in conjunction with the dimension.


NOTE: Figure 5 illustrates a structured dimension callout with both prefix and suffix information.


[[figure5]]
.Structured dimension callout
image::structured_dimension_callout.gif[Structured dimension callout]



[.underline]#EXPRESS specification:#



[source]
--
express_ref:[dimension_callout_component_relationship]
--

[[aic_draughting_elements.dimension_callout_relationship]]
==== dimension_callout_relationship


A *dimension_callout_relationship* is a type of
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.draughting_callout_relationship[draughting_callout_relationship]
that relates the presentation of a dimension to the presentation of the dimension callout either as the primary callout 
or as the secondary callout.
A primary callout is a 
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.draughting_callout[draughting_callout] 
that presents the dimension value in the primary unit of measure.
A secondary callout is a 
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.draughting_callout[draughting_callout] 
that presents the dimension value in another unit of measure.


[.underline]#EXPRESS specification:#



[source]
--
express_ref:[dimension_callout_relationship]
--

[[aic_draughting_elements.dimension_pair]]
==== dimension_pair


A *dimension_pair* is a type of
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.draughting_callout_relationship[draughting_callout_relationship]
that identifies the relationship between dimensions that participate in a chained or parallel dimension sequence.
A chained dimension sequence is a sequence of two or more dimensions in which the terminus of one dimension initializes 
the next dimension in the sequence.
A parallel dimension sequence is a collection of two or more dimensions where
all the dimensions are of the same type, their dimension lines are parallel to one another, the dimensions
share a common origin or datum, or all three.


NOTE: Figure 6 illustrates four horizontally-drawn linear dimensions in a series of parallel dimension pairs and three vertically-drawn linear dimensions in a series of parallel dimension pairs. Figure 7 illustrates three horizontally-drawn linear dimensions in a series of chained dimension pairs. In both figures, each set of two dimensions sharing a projection line is a dimension pair.


[[figure6]]
.Parallel dimension pair
image::parallel_dimension_pair.gif[Parallel dimension pair]


[[figure7]]
.Chain dimension pair
image::chain_dimension_pair.gif[Chain dimension pair]



[.underline]#EXPRESS specification:#



[source]
--
express_ref:[dimension_pair]
--

[[aic_draughting_elements.draughting_elements]]
==== draughting_elements


A *draughting_elements* is a type of
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.draughting_callout[draughting_callout]
that specifies constraints on the grouping of annotation within the context of draughting.
An application protocol that uses this AIC may ensure that the
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.draughting_callout[draughting_callout] 
entity is instantiated as a *draughting_elements* entity.


[.underline]#EXPRESS specification:#



[source]
--
express_ref:[draughting_elements]
--

[[aic_draughting_elements.geometrical_tolerance_callout]]
==== geometrical_tolerance_callout


A *geometrical_tolerance_callout* is a type of
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.draughting_callout[draughting_callout]
that presents a geometrical tolerance.


NOTE: The top view in Figure 3 illustrates the specification of a diameter dimension with an associated geometrical tolerance. The middle view illustrates a geometrical tolerance related by a projection line. Computer-interpretable geometric tolerances are outside the scope of this application interpreted construct.



[.underline]#EXPRESS specification:#



[source]
--
express_ref:[geometrical_tolerance_callout]
--

[[aic_draughting_elements.leader_directed_dimension]]
==== leader_directed_dimension


A *leader_directed_dimension* is a type of
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.leader_directed_callout[leader_directed_callout]
directed by a leader curve that presents some dimension value.


NOTE: Figure 8 illustrates a leader directed dimension used to depict information about the holes in the product. Linear dimensions are used to show the placement of the holes.


[[figure8]]
.Leader directed dimension
image::leader_directed_dimension.gif[Leader directed dimension]



[.underline]#EXPRESS specification:#



[source]
--
express_ref:[leader_directed_dimension]
--

[[aic_draughting_elements.linear_dimension]]
==== linear_dimension


A *linear_dimension* is a type of
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.dimension_curve_directed_callout[dimension_curve_directed_callout]
directed by a dimension curve that presents a value of distance between two elements, 
measured along a linear path, or the length of a linear element.


NOTE: Figures 3, 6, 7, and 8 show several linear dimensions used singularly or in dimension pairs.



[.underline]#EXPRESS specification:#



[source]
--
express_ref:[linear_dimension]
--

[[aic_draughting_elements.ordinate_dimension]]
==== ordinate_dimension


An *ordinate_dimension* is a type of
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.projection_directed_callout[projection_directed_callout]
directed by a projection curve that presents a dimension value.


NOTE: Figure 9 illustrates several ordinate dimensions used to dimension a simple mechanical product.


[[figure9]]
.Ordinate dimension
image::ordinate_dimension.gif[Ordinate dimension]



[.underline]#EXPRESS specification:#



[source]
--
express_ref:[ordinate_dimension]
--

[[aic_draughting_elements.radius_dimension]]
==== radius_dimension


A *radius_dimension* is a type of
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.dimension_curve_directed_callout[dimension_curve_directed_callout]
directed by a dimension curve that presents a value of the radial size of a circular element.


NOTE: Figure 1 illustrates a radius dimension. The figure also illustrates three angular dimensions.



[.underline]#EXPRESS specification:#



[source]
--
express_ref:[radius_dimension]
--

[[aic_draughting_elements.structured_dimension_callout]]
==== structured_dimension_callout


A *structured_dimension_callout* is a type of
../../../resource_docs/draughting/sys/5_schema.xml#draughting_element_schema.draughting_callout[draughting_callout]
that presents information associated with a
dimension, in which individual elements presenting different components of the dimensional information
may be identified and distinguished.


NOTE: Figure 5 illustrates components of a structured dimension callout. The dimension callout contains curves, symbols, and text. Text is identified as the dimension value, tolerance value, or unit text. Other draughting callouts can be identified as prefix or suffix information by use of <<aic_draughting_elements.dimension_callout_component_relationship>>.



[.underline]#EXPRESS specification:#



[source]
--
express_ref:[structured_dimension_callout]
--



[source]
--
*)
END_SCHEMA;  -- aic_draughting_elements
(*
--

[[AnnexA]]
[appendix,obligation=normative]
== Short names of entities

Requirements on the use of the short names are found in the implementation methods included in ISO 10303. EXPRESS entity names and the equivalent short names are available from:

[align=center]
http://standards.iso.org/iso/10303/tech/short_names/short-names.txt[http://standards.iso.org/iso/10303/tech/short_names/short-names.txt]

[[AnnexB]]
[appendix,obligation=normative]
== Information object registration

[[b1]]
=== Document Identification

To provide for unambiguous identification of an information object in an open system, the object identifier

[align=center]
{ iso standard 10303 part(506) version(3) }

is assigned to this part of ISO 10303. The meaning of this value is defined in ISO/IEC 8824-1, and is described in ISO 10303-1.

[[b2]]
=== Schema identification

==== aic-draughting-elements schema identification

To provide for unambiguous identification of the schema specifications given in this integrated resource in an open information system, the object identifiers are assigned as follows:

[align=center]
{ iso standard 10303 part(506) version(2) object(1) aic-draughting-elements(1) }

is assigned to the aic-draughting-elements schema. The meaning of this value is defined in ISO/IEC 8824-1, and is described in ISO 10303-1.

[[AnnexC]]
[appendix,obligation=informative]
== Computer interpretable listings

This annex references a listing of the EXPRESS entity names and corresponding short names as specified or referenced in this part of ISO 10303. It also provides a listing of each EXPRESS schema specified in this part of ISO 10303 without comments or other explanatory text. These listings are available in computer-interpretable form in Table C.1 and can be found at the following URLs:

Short names::: http://standards.iso.org/iso/10303/tech/short_names/short-names.txt[http://standards.iso.org/iso/10303/tech/short_names/short-names.txt]
EXPRESS::: http://standards.iso.org/iso/10303/smrl/v8/tech/smrlv8.zip[http://standards.iso.org/iso/10303/smrl/v8/tech/smrlv8.zip]

[#table_e1]
[cols="^,^",options="header"]
.EXPRESS listings
|===
| XML file | ASCII file

| c_exp_schema_4.xml[aic_draughting_elements.xml] | C:\Upwork\Metanorma\Stepmod\iso-10303-stepmod-master\data\resource_docs\draughting_elements\../../../data/resources/aic_draughting_elements/aic_draughting_elements.exp[aic_draughting_elements.exp]
|===



NOTE: The information provided in computer-interpretable form at the above URLs is informative. The information that is contained in the body of this part of ISO 10303 is normative.

[[AnnexD]]
[appendix,obligation=informative]
== EXPRESS-G diagrams

The diagrams in this annex correspond to the EXPRESS schemas specified in this part of ISO 10303. The diagrams use the EXPRESS-G graphical notation for the EXPRESS language. EXPRESS-G is defined in ISO 10303-11.

* <<aic_draughting_elementsexpg1,Figure D.1 — EXPRESS-G diagram of the aic_draughting_elements (1 of 2)>>;

* <<aic_draughting_elementsexpg2,Figure D.2 — EXPRESS-G diagram of the aic_draughting_elements (2 of 2)>>.



[[AnnexE]]
[appendix,obligation=informative]
== Change history

[[general]]
=== General

This annex documents the history of technical modifications made to ISO/TS 10303-506.

Unless otherwise specified all modifications are upwardly compatible to 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 of ISO 10303, also conform to a revision of that application protocol based on this edition of this part of ISO 10303;

* interfaces that conform to ISO 10303-22 and to an ISO 10303 application protocol based on the previous edition of this part of ISO 10303, also conform to a revision of that application protocol based on this edition of this part of ISO 10303;

* the mapping tables of ISO 10303 application protocols based on the previous edition of this part of ISO 10303 remain valid in a revision of that application protocol based on this edition of this part of ISO 10303.

[[change_2]]
=== Changes made in edition 2

[[summary2]]
==== Summary of changes

The second edition of this part of ISO 10303 incorporated the modifications to the first edition listed below.

[[schema.changes2]]
==== Changes made to schema aic_draughting_elements

The following EXPRESS declarations and interface specifications have been modified:

* ENTITY draughting_elements;

* ENTITY leader_directed_dimension.

[[change_3]]
=== Changes made in edition 3

[[summary3]]
==== Summary of changes

This third edition of this part of ISO 10303 incorporates the modifications to the second edition listed below.

The constraint on AP application of this AIC with respect to draughting elements has been removed.

NOTE: The change occurred in a description in ENTITY type *draughting_elements* and no EXPRESS changes were made in the *aic_draughting_elements*. Because no EXPRESS declarations were modified, the aic_draughting_elements schema version identifier was not changed.

[[bibliography]]
== Bibliography

* [[[ref8824-1,ISO/IEC 8824-1]]], _Information technology -- Abstract Syntax Notation One (ASN.1) -- Part 1: Specification of basic notation_