PDM-UG: Substitute Components in an Assembly
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This page belongs to the PDM Usage Guide.
Substitute components in an assembly are identified as a relationship between the occurrences of two part definitions (the two substitutes) that are used within the same parent assembly definition. As opposed to the alternate part relationship, which is context free, this substitute relationship is context dependent - the substitute is only valid in the context of its usage as a component within the specified parent assembly definition.
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The Instance Model: EXPRESS entities and attributes
The EXPRESS entities and attributes used to support the requirements of substitute part identification are illustrated in Diagram 29.
Diagram 29: Substitute Component Instance Diagram
Assembly component usage substitute
The assembly_component_usage_substitute entity represents the substitute component relationship. The substitute part is interchangeable with the base part only in the particular, specified usage - it is a context dependent substitution that is allowed only in the specific usage as the component in the identified component-assembly relationship.
Attributes
- The name attribute has no standard mapping in the PDM Schema.
- The definition attribute is an optional description.
- The base attribute is a reference to the primary component occurrence of which a substitute is being identified.
- The substitute attribute is a reference to the product identified as a substitute for the base component.
| ENTITY assembly_component_usage_substitute | Attribute Population | Remarks |
| name | type : label = string | |
| definition | type : text = string | OPTIONAL |
| base | type : entity = assembly_component_usage | |
| substitute | Type : entity = assembly_component_usage |
===Preprocessor Recommendations=== There are no standard mappings for the name and definition attributes of assembly_component_usage_substitute. The relating_product_definition for both the base and substitute attributes of this relationship must be the same instance representing the same assembly definition.
===Postprocessor Recommendations=== Since there are no standard mappings for the name and definition attributes of assembly_component_usage_substitute, it is recommended that postprocessors not assign any general processing significance to these values.
===Related Entities=== None specified.
The Instance Model: STEP exchange file format (ISO10303 Part 21 syntax)
#1330 = PROMISSORY_USAGE_OCCURRENCE('seal_in_sleeve', 'single instance usage', 'promissory usage of sealing for sleeve assembly ver2', #1210, #1300, $);
#1335 = PROMISSORY_USAGE_OCCURRENCE('seal_in_sleeve', 'single instance usage', 'promissory usage of sealing ver 2 for sleeve assembly ver2', #1210, #1305, $);
#1337 = ASSEMBLY_COMPONENT_USAGE_SUBSTITUTE('sealings_alternative_sleeve', $,#1330,#1335);
