PDM-UG: Explicit Representation of Complete Assembly Geometry
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This approach represents the assembled model completely. It is appropriate for explicit representation of assemblies. It uses mapped_item in combination with repesentation_map, which takes a representation and turns it into an item in a second representation. The transformation to be applied is determined from the mapping origin and the mapping target, which are items in the two representations (and therefore founded in the two contexts).
Mapped_item is constrained such that:
- No mapped item shall be dependent on itself to define the representation being mapped (a cyclic).
- The mapping origin shall be in the context of the mapping_source representation.
There is no constraint to prevent both representations having the same context (i.e., the new item is shifted in position but does not change spaces). This allows the use of mapped_item to position sub-models in a single coordinate space. It is even possible to define an identity matrix transformation by referring to the same entity instance as both mapping_origin and mapping_target. This represents the case where a component is defined in (one of) its final position(s). Until it is mapped into the second representation, it is not included in the representation even though defined in the same space.
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The Instance Model: EXPRESS entities and attributes
The EXPRESS entities and attributes used to support the requirements of explicit representation of assembly structure with associated external geometry model structure are illustrated in Diagram 25.
Diagram 25: Assembly Structure with Component Templates Instance Diagram
Mapped item
The mapped_item allows the use of a representation as a representation_item, e.g., it allows for the definition of representation using other representations. Thus a shape_representation for an assembly component can participate as a template instance in the definition of the shape of the overall assembly. The representation is defined by mapped_item.mapping_source.mapped_representation. The mapping is achieved through an operator that is a mapping of the mapped_item. mapping_source.mapping_origin onto the mapped_item.mapping_target.
Attributes
- The mapping_source attribute points to an instance of representation_map that specifies the to be mapped representation.
- The mapping_target attribute is an representation_item that defines.
| ENTITY mapped_item | Attribute Population | Remarks |
| mapping_source | type: entity = representation_map | |
| mapping_target | type: entity = representation_item |
===Preprocessor Recommendations=== None specified.
===Postprocessor Recommendations=== None specified.
===Related Entities=== None specified.
Representation map
Attributes
- The mapping_origin attribute.
- The mapped_representation attribute references the to be mapped representation.
| ENTITY representation_map | Attribute Population | Remarks |
| mapping_origin | type: entity = representation_item | should be an axis_placement in the given context |
| mapped_representation | type: entity = representation |
===Preprocessor Recommendations=== None specified.
===Postprocessor Recommendations=== None specified.
===Related Entities=== None specified.
