PDM-UG: Alternate Parts
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This page belongs to the PDM Usage Guide.
STEP designates alternate and substitute parts differently. Alternate parts are interchangeable in all occurrences whereas substitutes are interchangeable only in a particular usage. Alternate parts in STEP are defined through the alternate_product_relationship entity. This relationship is used in the definition of parts list data for alternate item designations.
Contents |
The Instance Model: EXPRESS entities and attributes
The EXPRESS entities and attributes used to support the requirements of alternate part identification are illustrated in Diagram 28.
Diagram 28: Alternate Part Instance Diagram
Alternate product relationship
The alternate_product_relationship entity represents the alternate part relationship. The alternate part is interchangeable with the base part in any/all uses - it is a context independent alternate that is form, fit, and function equivalent in any use.
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 product of which an alternate is being identified.
- The alternate attribute is a reference to the product identified as an alternate for the base product.
- The basis attribute is a rationale for the part interchange (e.g., any use, first available, etc.).
| ENTITY alternate_product_relationship | Attribute Population | Remarks |
| name | type : label = string | |
| definition | type : text = string | OPTIONAL |
| base | type : entity = product | |
| alternate | type : entity = product | |
| basis | type : text = string |
===Preprocessor Recommendations=== There are no standard mappings for the name and definition attributes of alternate_product_relationship. The basis attribute should contain a rationale for the part interchange (e.g. any use, first available, etc.) if it is known.
===Postprocessor Recommendations=== Since there are no standard mappings for the name and definition attributes of alternate_product_relationship, 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)
/* primary application context for design assembly life cycle */
#10 = APPLICATION_CONTEXT('mechanical design');
#220 = PRODUCT_CONTEXT('', #10, '');
#230 = PRODUCT_DEFINITION_CONTEXT('part definition', #10, 'design');
/* part type discrimination */
#6=PRODUCT_RELATED_PRODUCT_CATEGORY('part',$,(#4, #11));
#7=PRODUCT_CATEGORY_RELATIONSHIP('part-to-detail',$,#6,#8);
#8=PRODUCT_RELATED_PRODUCT_CATEGORY('detail',$,(#4, #11));
#4=PRODUCT('11111','Solid Box','description for part 11111',(#220));
#11=PRODUCT('11011','Solid Cube','description for part 11011',(#12));
#14=ALTERNATE_PRODUCT_RELATIONSHIP('',$,#11,#4,'interchangeable as solid squares');
