Basic Drawing Organization

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This page belongs to the Recommended Practices for the Presentation of GD&T.

Scope

This page focuses on drawings which can be printed on paper or being presented on a computer monitor.

the identification of a drawing and its linking to products
the decomposition of a drawing into pages
the decomposition of a drawing page into views, annotations and a drawing frame

The structure defined here is also suitable to support the high level concepts as defined in ISO 16792, Technical product documentation â€�? Digital product definition data practices. For this a saved view is taken as a drawing page and the set of all saved views is taken as a drawing.

Recommendations are given on how to use entities from the

presentation_organization_schema defined in ISO 10303-46 Visual presentation and the
drawing_definition_schema defined in ISO 10303-101 Draughting

as used by the APs 201, 202, 203ed2, and 214. These APs supports a common high level drawing structure which is described here.

This page does not cover further specializations originally defined in edition 1 of AP201:1994 and AP202:1996 and then later wrapped by the

aic_drawing_structure_and_administration defined in ISO 10303-505 Drawing structure and administration but not used in further APs.

Prerequisites

You should be familiar with the following:

Product Basics
The representation schema and in particular mapped_item
basic geometry

General about presentation hierarchy as defined in ISO 10303-46

Looking to figure 1 we can see in the upper right the root entities from part43 ( representation, representation_item, representation_context) together with mapped_item and representation map to include lower-level representations as definitional part into higher-level representations. These entities are further specialized in part 46 for presentation purposes.

First we have presentation_representation <= representation. It has a rule to enforce having a 2D geometric_representation_context. The two main subtypes are presentation_area and presentation_view.

A presentation_area is a kind of a picture. It is either a top level picture and as such related to a presentation_set or it is a sub-picture included in a higher level presentation_area . A presentation_area is always clipped by a planar_box assigned with presentation_size, either directly or only in its usage in area_in_set. If a lower-level presentation_area is included in an upper-level presentation area then the clipping region of the upper level presentation_area applies also for the lower level ones.

A presentation_set is a collection of one or more (top) presentation_areas. Either the presentation_set or any of the presentation_representations can be related to some other STEP entities via presented_item_representation and presented_item. Presented_item is abstract and needs to be further sub-typed to refer to the specific to other STEP entities.

While a presentation_area stands for a complete picture, a presentation_view stands for a partial incomplete picture. A presentation_view must always be part of some presentation_area.

Figure 1. Drawing structure entities

Drawing hierarchy as defined in ISO 10303-101

Part 101 of STEP Draughting defines specializations of the entities mentioned above for the purpose of drawing. A drawing may be on paper or on a computer screen. So also when a 3D model is displayed on the 2D screen of a computer in a specific orientation, scale, and projection we will take this as a drawing; even if the user can then interactively change the visible picture by e.g. rotating the 3D model.

The drawing hierarchy as defined in part 101 is a specialization and extension of the more general presentation hierarchy in IR46. The data is typically processed in this way:

Alternatively one may start with drawing_definition which is the former root entity for drawings. It may lead you to 0, 1 or more drawing_revision and you would need to decide which one to use if there are several. A drawing_revision_sequence (not shown here) may help you to get the most recent one. A drawing_definition gives an identifier for the organizational number of a drawing and specifies a label for the categorization of a drawing. Now with the Document-as-product approach it is recommended for the parsing of STEP datasets to start from from product or product_concept as it is also the case for datasets without drawings.

A product_definition_formation is the recommended local start point for this page. Via the linking entity instances applied_presented_item (or draughting_presented_item for AP201ed1 and AP202ed1, both <= presented_item) and presented_item_representation you will find your drawing_revision if present. It is recommended to not link more than one drawing_revision to a product_definition_formation.

A drawing_revision (<= presentation_set) represent the top entity for a drawing of a particular version. For AP201ed1 and AP202ed2 the subtype draughting_drawing_revision is to be used. A drawing_revision may get a single title (see restrict_drawing.wr2) via draughting_title. The particular revision of this drawing is identified via the attribute revision_identifier. The revision identifier must be unique for the referenced drawing_definition (see drawing_revision.ur1).

A revision of a drawing includes one or more (see restrict_drawing.wr1) revisions of sheets drawing_sheet_revision that are part of the drawing. They are linked via drawing_sheet_revision_usage. The attribute drawing_sheet_revision_usage.sheet_number tells you the particular sheet number (e.g. "1", "2", "3" ...). The sheet numbers don't need to start with "1" and in principle any kind of string can be used (e.g. "first page"). The only requirement is that the sheet numbers are unique for a drawing_revision (see drawing_sheet_revision_usage.ur1). A drawing_sheet_revision is a sheet with an assigned revision identifier (attribute revision_identifier). If no revision identifier is available an empty string is to be used.

A drawing_sheet_revision (<= presentation_area <= presentation_representation <= representation) identifies a single sheet of a drawing_revision. It may have a title given by an instance of draughting_title. Also it must have its own geometric_representation_context which is not shared by any other representation. The content of a drawing_sheet_annotation may consist of one or more presentation_view (via mapped_item), at most one xxxxxxxxxxx which where further sub-divided into one or several

presentation_view with the 2D drawing content which could come from a 2D or 3D model and annotations.

The items of a drawing sheet include an axis2_placement_2d that is the origin of the sheet, mapped_items) that place presentations on the sheet, and a planar_box that defines the size of the sheet. Drawing sheets may also contain annotation_occurrences that are defined and depicted in the sheet.

History

Back in 1994 when AP201 was standardized drawings were designed as standalone entities which may or may not be related to some product. This concept was also driven forward by AIC 505. But with the release of AP214 in 2001 and the introduction of the document as product concept this direction was given up. Now a drawing can be related to these specializations of products:

Part_version when it is describing a typical product (Item_version in AP214-ARM)
Product_as_individual_version when it is a describing a particular physical realized or planed product (the product_definition_formation of a Physical_instance in AP214), or to a
Document_version representing and wrapping up this particular drawing (same in AP214-ARM).

Example

Figure 2. Example drawing structure instances

#95=PRODUCT_DEFINITION_FORMATION('1',...);
 
#10400=PRESENTATION_VIEW('Front view',(#10410, #10323),#10401);
#10401=(GEOMETRIC_REPRESENTATION_CONTEXT(2)
        GLOBAL_UNIT_ASSIGNED_CONTEXT((#4,#10402))
        REPRESENTATION_CONTEXT('2D coordinate system context','2D'));
#10402=(CONVERSION_BASED_UNIT('DEGREE',#10403)NAMED_UNIT(#10404)PLANE_ANGLE_UNIT());
#10403=PLANE_ANGLE_MEASURE_WITH_UNIT(PLANE_ANGLE_MEASURE(0.0174532925),#10405);
#10404=DIMENSIONAL_EXPONENTS(0.,0.,0.,0.,0.,0.,0.);
#10405=(NAMED_UNIT(*)PLANE_ANGLE_UNIT()SI_UNIT($,.RADIAN.));

#10410=(CAMERA_IMAGE()
        CAMERA_IMAGE_3D_WITH_SCALE()
        GEOMETRIC_REPRESENTATION_ITEM()
        MAPPED_ITEM(#10310,#10411)
        REPRESENTATION_ITEM());
#10411=PLANAR_BOX(,5.,5.,#10412);
#10412=AXIS2_PLACEMENT_2D(,#10413,#10414);
#10413=CARTESIAN_POINT(,(0.,0.));
#10414=DIRECTION(,(1.,0.));

#10500=DRAWING_SHEET_REVISION('Sheet 1',(#10501,#10510,#10521),#10504,'-');
#10501=AXIS2_PLACEMENT_2D(,#10502,#10503);
#10502=CARTESIAN_POINT(,(0.0,0.0));
#10503=DIRECTION(,(1.0,0.0));
#10504=(GEOMETRIC_REPRESENTATION_CONTEXT(2)
        GLOBAL_UNIT_ASSIGNED_CONTEXT((#4,#10402))
        REPRESENTATION_CONTEXT('2D coordinate system context','2D'));
#10505=DRAUGHTING_TITLE((#10500),'English','Sheet 1');
#10510=MAPPED_ITEM(,#10511,#10501);
#10511=REPRESENTATION_MAP(#10323,#10400);
#10520=PRESENTATION_SIZE(#10500,#10521);
#10521=PLANAR_BOX(,10.0,10.0,#10522);
#10522=AXIS2_PLACEMENT_2D(,#10523,#10524);
#10523=CARTESIAN_POINT(,(0.0,0.0));
#10524=DIRECTION(,(1.0,0.0));

#10600=DRAWING_DEFINITION('Drawing of product_0',$);
#10601=DRAWING_REVISION('A',#10600,$);
#10602=DRAUGHTING_TITLE((#10601),'English','Associative dimension test part');
#10603=DRAUGHTING_PRESENTED_ITEM((#95));
#10604=PRESENTED_ITEM_REPRESENTATION(#10601,#10603);
#10605=DRAWING_SHEET_REVISION_USAGE(#10500,#10601,'1');

Complete Part21 example can be found here callouts.stp

Constraints

The instance pattern presented on this slide is enforced by a couple of rules. In AP201ed1 and AP202ed1 most of the rules are defined for in draughting_drawing_revision which is a subtype of drawing_revision. In AP214 and the upcoming AP203ed2 they are define in the global rule restrict_drawing:

Each drawing_revision shall be related to at least one presentation_area, each of which is a drawing_sheet_revision.
Each drawing_revision shall be one of the items of no more than one draughting_title.
Each sheet of the drawing_revision shall be one of the items of no more than one draughting_title.
The items of each sheet of the drawing_revision shall be a styled_item, a mapped_item, an axis2_placement, or a planar_box.
The items of each sheet of the drawing_revision shall include at least one styled_item or mapped_item.
Each sheet of the drawing_revision shall contain exactly one planar_box that is the size of a presentation_size.
If there is a mapped_item in a sheet of the drawing_revision, the source of the mapped_item shall be a presentation_view.
Every axis2_placement in a sheet of the drawing_revision shall be the mapping_target for some mapped_item. It is recommended to not include those instances of axis2_placement in drawing_sheet_revision.items at all.
The representation_context of a sheet of the drawing_revision shall not be the context of any other representation.
Each view in a sheet of the drawing_revision shall be the mapped_representation for exactly one mapped_item. Together with rule 7 this ensures that a presentation_view is used only once (LK is this really good?)
The items of each view of each sheet of the drawing_revision shall be a styled_item, a camera_image, or an axis2_placement.
Each view of each sheet of the drawing_revision shall contain exactly one axis2_placement which is the mapping_origin for a mapped_item.
The representation_context of each view of each sheet of the drawing_revision shall not be the context of any other representation.

5.2.4.54 drawing_sheet_annotation_layers

The drawing_sheet_annotation_layers rule ensures that every annotation_occurrence that is an item in a drawing_sheet_revision is assigned to at least one layer. WR1: Every item of each drawing_sheet_revision that is an annotation_occurrence shall be one of the assigned_items of at least one presentation_layer_assignment. WR1: Each mapped_item that is the mapping of a drawing_sheet_layout shall be one of the items in a drawing_sheet_revision.

5.2.4.55 drawing_sheet_layout_usage

The drawing_sheet_layout_usage rule ensures that a drawing_sheet_layout is mapped as one of the items of a drawing_sheet_revision.

5.2.3.1.59 drawing_sheet_layout

A drawing_sheet_layout is a symbol that presents the layout or format for a drawing sheet. WR1: Each mapped_item that is the mapping of a drawing_sheet_layout shall be one of the items in a drawing_sheet_revision.

5.2.4.214 sheets_belong_to_one_drawing

The sheets_belong_to_one_drawing rule ensures that each drawing_sheet_revision belongs to exactly one drawing_revision. WR1: For each instance of drawing_sheet_revision there shall be exactly one instance of drawing_sheet_revision_usage which contains the instance of drawing_sheet_revision as its area attribute.

Entities and Attributes

Name	Explanation
presentation_size	Used to define the size of a presentation_view or presentation_area.
unit	The representation that is being assigned a size. In our scope this is the drawing_sheet_revision.
size	A planar_box that describes the size of the unit attribute.
drawing_definition	Identifies a set of drawing revisions.
drawing_number	The organizational number assigned to the drawing (identifier).
drawing_type	A label used to categorize the drawing. Due to no requirement defined, it is recommended to instantiate with an empty string.
drawing_revision	A revision of a drawing.
revision_identifier	The identifier of the drawing revision, usually a letter revision designator.
drawing_identifier	The identifier of a drawing (a pointer to the drawing_definition).
intended_scale	Optional: a text description of the intended scale â€“ for information only.
draughting_title	A brief text string describing the contents of the drawing.
items	The sheets or revisions to which the description applies.
language	A label to define the language of the description.
contents	The text description.
draughting_presented_item	Assigns an item to a presentation_representation or a presentation_set.
items	The set of assigned items. Within our scope, this set only includes product_definitions.
presented_item_representation	The association of a presentation with the item for which its is the picture.
presentation	The presentation.
item	The presented item.
drawing_sheet_revision	A revision of a drawing sheet.
name	The organizational name assigned to the drawing sheet.
items	The elements of the sheet. In our context this includes the axis2_placement_2d that is the origin of the sheet, mapped_items that place presentations on the sheet, and a planar_box that defines the size of the sheet.
context_of_items	A two-dimensional representation context.
revision_identifier	The organizational identifier assigned to the drawing sheet.
drawing_sheet_revision_usage	Relates the revision of a sheet with the revision of a drawing.
area	The drawing_sheet_revision.
in_set	The drawing_revision.
sheet_number	An identifier indicating the position of the sheet in the overall sequence of sheets defining the drawing.

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