PDM-UG: Relating Part Shape
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The Instance Model: EXPRESS entities and attributes
The EXPRESS entities and attributes used to support the requirements of relating shape representations is illustrated in Diagram 12.
Shape representation relationship
The entity shape_representation_relationship_is a subtype of representation_relationship. The subtype adds specific local constraints that ensures that it defines a relationship between two shape_representations. To define a relationship between two shape_representations that is established via a transformation, a complex instantiation of shape_representation_relationship AND representation_relationship_with_transformation is used.
Attributes
- The name attribute is used to name the relationship. The name of the relationship can be used to indicate the type of the relationship established. Relationships may be established to capture semantics as ‘is derived from’, ‘should be oriented against’ or ‘decomposition’.
- The description attribute can be used to provide optional further textual description.
- The rep_1 attribute references the first of the related shape_representations.
- The rep_2 attribute references the second of the related shape_representations.
| ENTITY shape_representation_relationship | Attribute Population | Remarks |
| name | type: label = string | May characterize the type of the relationship |
| description | type: text = string | OPTIONAL |
| rep_1 | type: entity = shape_representation | |
| rep_2 | Type: entity = shape_representation |
===Preprocessor Recommendations=== The meaning of the rep_1 and rep_2 attributes is specified further by the relation type indicated by the attribute shape_representation_relationship.name.
===Postprocessor Recommendations=== None specified.
===Related Entities=== None specified.
Representation relationship with transformation
The entity representation_relationship_with_transformation_is a subtype of representation_relationship. The subtype adds the attribute transformation_operator as a reference to a transformation. To define a relationship between two shape_representations that is established via a transformation, a complex instantiation of shape_representation_relationship AND representation_relationship_with_transformation is used.
NOTE - A shape_representation_relationship between instances of shape_representation does not necessarily imply a relationship in the sense of decomposition of a given part shape. A decomposition type of relationship can be assumed when shape_representations which are linked to shape_aspects of a product_definition_shape are related to a shape_representation declared to represent the same product_definition_shape in total, i.e., a shape_representation linked to the product_definition_shape with an instance of shape_definition_representation.
Attributes
- The name attribute is used to name the relationship and may characterize the relation type.
- The description attribute can be used to provide optional further textual description.
- The rep_1 attribute references the first of the related shape_representations.
- The rep_2 attribute references the second of the related shape_representations.
- The transformation_operator attribute specifies the transformation operator that defines the relationship.
| ENTITY shape_representation_relationship | Attribute Population | Remarks |
| name | See shape_representation_relationship | |
| description | See shape_representation_relationship | OPTIONAL |
| rep_1 | See shape_representation_relationship | |
| rep_2 | See shape_representation_relationship | |
| transformation_operator | type: entity item_defined_transformation or functionally_defined_transformation |
===Preprocessor Recommendations=== None specified.
===Postprocessor Recommendations=== None specified.
===Related Entities=== None specified.
