Associativity between GD&T and its presentation

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

Detailed GD&T representation and presentation data is linked together with shape_aspect_associativity (#11000). The relating shape_aspect (#11010) captures the portions of a geometric model that are to be associated with annotation. The related shape_aspect (#11020) captures the annotation elements that are to be associated with elements of a geometric model. Both shape_aspects have to share the same product_definition_shape (#97).

In principle there are 2 approaches possible

• pattern to use with STEP standards released till 2005
• pattern to use with STEP standards from 2007 on

Associativity for AP203-TS/2005 and AP214ed2/2003

In the current STEP schemas (AP203, AP214) only old approach is possible. Example of it is provided in Figure 1. This diagram shows the way to associate leader_directed_callout (#200) with edge_curve (#10074) it is representing. Besides shape_aspect_associativity and shape_aspect mentioned above, user has to also populate many intermediate entities - property_definition (#11013 and #11023), shape_definition_representation (#11012 and #11022) and shape_representation (#11011 and #11021).

Figure 1. Associativity between a portion of the geometry (edge_curve) and annotation (the draughting_callout), using old, currently available approach.

#96=PRODUCT_DEFINITION(' ',' ',#95,#92);
#97=PRODUCT_DEFINITION_SHAPE(' ',' ',#96);
#200=LEADER_DIRECTED_CALLOUT('callout',(#205,#173,#400));
#10074=EDGE_CURVE(,#10011,#10013,#10029,.T.);
#10123=ORIENTED_EDGE(' ',*,*,#10074,.T.);
#10126=EDGE_LOOP(' ',(#10122,#10123,#10124,#10125));
#10127=FACE_OUTER_BOUND(' ',#10126,.T.);
#10133=ADVANCED_FACE(' ',(#10127),#10132,.T.);
#10158=CLOSED_SHELL(' ',(#10097,#10109,#10121,#10133,#10145,#10157));
#10159=MANIFOLD_SOLID_BREP(' ',#10158);
#10167=(GEOMETRIC_REPRESENTATION_CONTEXT(3)GLOBAL_UNCERTAINTY_ASSIGNED_CONTEXT((#10166))
 GLOBAL_UNIT_ASSIGNED_CONTEXT((#4,#5,#3))REPRESENTATION_CONTEXT('MASTER','3D'));
#10168=ADVANCED_BREP_SHAPE_REPRESENTATION(' ',(#10159),#10167);
#10198=SHAPE_DEFINITION_REPRESENTATION(#97,#10168);
#10300=DRAUGHTING_MODEL('Leader curve callout',(#200, #10311),#10167);
#11000=SHAPE_ASPECT_ASSOCIATIVITY('link edge curve with callout pointing to it', $, #11010, #11020);
#11010=SHAPE_ASPECT('edge to highlight',$,#97,.T.);
#11011=SHAPE_REPRESENTATION('edge to highlight', (#10074), #10167);
#11012=SHAPE_DEFINITION_REPRESENTATION(#11013,#11011);
#11013=PROPERTY_DEFINITION('edge to highlight',$,#11010);
#11020=SHAPE_ASPECT('callout to pick',$,#97,.F.);
#11021=SHAPE_REPRESENTATION('callout to pick', (#200), #10167);
#11022=SHAPE_DEFINITION_REPRESENTATION(#11023,#11021);
#11023=PROPERTY_DEFINITION('callout to pick',$,#11020);

Complete Part21 example can be found here callouts.stp.

Associativity for upcoming AP203ed2/2007

It is clear that currently available structure is not optimal and partially redundand. It was recognized that item_identified_representation_usage entity allows to simplify it a lot. Instead of 3 entities ( property_definition, shape_definition_representation and shape_representation) we need to populate just one - item_identified_representation_usage. In the case of previously provided example, instead of having 6 intermediate entities we have only 2 item_identified_representation_usages (#11030 and #11040). So when this new pattern is allowed by Application Protocal - it is recommended to use it (Figure 2) rather than pattern provided in Figure 1. In order to distinguish item_identified_representation_usages used to link draughting_model from the one pointing to geomeric model (in this case A-BREP), 2 specific subtypes were introduced: draughting_model_item_association and geometric_item_specific_usage respectively. Complete Part21 example can be found here callouts.stp.

Figure 2. Associativity between a portion of the geometry (edge_curve) and annotation (the draughting_callout), using new approach.

#96=PRODUCT_DEFINITION(' ',' ',#95,#92);
#97=PRODUCT_DEFINITION_SHAPE(' ',' ',#96);
#200=LEADER_DIRECTED_CALLOUT('callout',(#205,#173,#400));
#10074=EDGE_CURVE(' ',#10011,#10013,#10029,.T.);
#10123=ORIENTED_EDGE(' ',*,*,#10074,.T.);
#10126=EDGE_LOOP(' ',(#10122,#10123,#10124,#10125));
#10127=FACE_OUTER_BOUND(' ',#10126,.T.);
#10133=ADVANCED_FACE(' ',(#10127),#10132,.T.);
#10158=CLOSED_SHELL(' ',(#10097,#10109,#10121,#10133,#10145,#10157));
#10159=MANIFOLD_SOLID_BREP(' ',#10158);
#10167=(GEOMETRIC_REPRESENTATION_CONTEXT(3)GLOBAL_UNCERTAINTY_ASSIGNED_CONTEXT((#10166))
 GLOBAL_UNIT_ASSIGNED_CONTEXT((#4,#5,#3))REPRESENTATION_CONTEXT('MASTER','3D'));
#10168=ADVANCED_BREP_SHAPE_REPRESENTATION(' ',(#10159),#10167);
#10198=SHAPE_DEFINITION_REPRESENTATION(#97,#10168);
#10300=DRAUGHTING_MODEL('Leader curve callout',(#200, #10311),#10167);

#11010=SHAPE_ASPECT('edge to highlight',$,#97,.T.);
#11030=GEOMETRIC_ITEM_SPECIFIC_USAGE(' ',$, #11010, #10168, #10074);
#11040=DRAUGHTING_MODEL_ITEM_ASSOCIATION(' ',$, #11010, #10300, #200);

Complete Part21 example can be found here callouts.stp.

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