PDM-UG: Implicitly defined transformations between geometric models

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This page belongs to the PDM Usage Guide.

A relationship can be defined implicitly by referencing an item_defined_transformation that has two reference points to specify origin and target of the transformation.

The Instance Model: EXPRESS entities and attributes

The EXPRESS entities and attributes used to support the requirements of implicit definition of transformation between the elements of two representations are illustrated in Diagram 14.

Diagram 14: Implicitly Defined Geometric Relations Instance Diagram

Item defined transformation

An item_defined_transformation models a transformation performed by defining two representation_items before and after applying the transformation function The transformation function is not explicitly provided, but it is derived through its relationship to the representation_items.

Attributes

• The name attribute provides a name for the transformation.
• The description attribute can be used to provide optional further textual description.
• The transform_item_1 references the first item (origin for the transformation).
• The transform_item_2 attribute references the second item (target for the transformation).

ENTITY item_defined_transformation	Attribute Population	Remarks
name	type: label = string
description	type: text = string	OPTIONAL
transform_item_1	type: entity = representation_item	here: axis2_placement_3d
transform_item_2	type: entity = representation_item	here: axis2_placement_3d

===Preprocessor Recommendations=== To be meaningful the item_defined_trasnformation with axis2_placement_3d requires that the representations that include transfrom_item_1 and transform_item_2 share the same geometric_representation_context.

===Postprocessor Recommendations=== None specified.

===Related Entities=== None specified.