PDM-UG: Different Views on Assembly Structure
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This page belongs to the PDM Usage Guide.
Different view definitions of the same version of a part may participate in different explicit product structures in the PDM Schema. For example, a design/as-planned view of a particular version of a part, representing the design discipline part definition, may be engaged in an explicit design assembly structure. A manufacturing/as-built view of the same part version represents the definitional template for the actual physical part, and may participate in a manufactured assembly structure different from the design structure. Finally, a support/as-maintained view of the part version representing the physical part definition that may participate in yet another different disassembly structure. Figure 7 illustrates two different views on a part structure.
Figure 7: Different Views on Assembly Structure
Many of the parts that make up the 'nodes' in the two different assembly structures in Figure 7 have the same base identification - they simply have multiple definitions from different life-cycle viewpoints. The disc with holes, the cap, and the sleeve sub-assembly are all present in both views of the part structure. However, in this example there is also a new 'node' in the disassembly structure. It corresponds to a sub-assembly, composed of a disc with holes and a cap, which was not present in the assembly structure (see Figure 8).
Figure 8: Different Indentured Lists Corresponding to Different Structure Views
The Instance Model: EXPRESS entities and attributes
The EXPRESS entities and relationships that support the requirements of alternate life-cycle viewpoints on product structure are the same as those already described for part structures. Recall that the structural element of the part master 'node' is the product_definition entity, representing a view definition of a part version. The previous description presumed that each part master element in the assembly structure had a consistent life-cycle view definition - a single assembly structure from a single view definition context.
In this example of multiple part structures, the part master information corresponding to the 'nodes' disc with holes and cap (and sleeve sub-assembly plus its components) each has two part view definitions. One view definition may represent, for example, the design or manufactured assembly structure; the other a maintenance or disposal disassembly structure. Both of the view definitions are related to the same part version. In this way, the information that is common across the different part structures (the base version identification for all 'nodes' that have definition in both structures) is represented only once. Information that is different between the different views, such as associated management data, property information, or in this case product structure itself is managed independently by using different product_definitions.
The assembly structure would be constructed between the product_definition instances that represent the part view definitions within the same appropriate view context, say for example design.
The disassembly structure would also be constructed between product_definition instances representing part view definitions within one appropriate life-cycle stage - but a different one, for example maintenance. Present only in the disassembly structure, the new or "phantom" part is a sub-assembly composed of a disc with holes and a cap - it is not present in the assembly structure. The part master information corresponding to this discap sub-assembly need only have a single part view definition in the appropriate life-cycle stage, e.g., maintenance. The complete disassembly structure is constructed using this product_definition, along with those of the other component part masters for that same view context.
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');
/* primary application context for maintenance disassembly view */
#110 = APPLICATION_CONTEXT('maintenance planning');
#240 = PRODUCT_DEFINITION_CONTEXT('part definition', #110, 'maintenance');
/* optional AP214 specific characterization for assembly definitions */
#340 = PRODUCT_DEFINITION_CONTEXT_ROLE('part definition type', $);
#350 = PRODUCT_DEFINITION_CONTEXT('assembly definition', #10, '');
#820 = PRODUCT_DEFINITION_CONTEXT_ASSOCIATION(#460, #350, #340);
#830 = PRODUCT_DEFINITION_CONTEXT_ASSOCIATION(#660, #350, #340);
/* type discriminator for part as product */
#100 = PRODUCT_RELATED_PRODUCT_CATEGORY('part', $, (#380, #680, #440, #640));
#360 = PRODUCT_RELATED_PRODUCT_CATEGORY('detail', $, (#380, #680));
#420 = PRODUCT_RELATED_PRODUCT_CATEGORY('assembly', $, (#440, #640));
/* part master for common components, each with two view definitions */
/* part master for disc with holes - two view definitions */
#380 = PRODUCT('d1', 'disc with holes', $, (#220));
#390 = PRODUCT_DEFINITION_FORMATION('A','',#380);
#400 = PRODUCT_DEFINITION('dvd1', 'design view on disc', #390, #230);
#410 = PRODUCT_DEFINITION('mvd1', 'maintenance view on disc', #390, #240);
/* part master for cap component - two view definitions */
#680 = PRODUCT('cap1', 'cap for hub', $, (#220));
#690 = PRODUCT_DEFINITION_FORMATION('A','',#680);
#700 = PRODUCT_DEFINITION('dvc1', 'design view on cap', #690, #230);
#710 = PRODUCT_DEFINITION('mvc1', 'maintenance view on cap', #690, #240);
/* part master for "phantom" sub-assembly definition - one view only */
#440 = PRODUCT('p1', 'hubcap subassembly', $, (#220));
#450 = PRODUCT_DEFINITION_FORMATION('A','',#440);
#460 = PRODUCT_DEFINITION('mvp1', 'maintenance view hubcap disassembly', #450, #240);
/* part master for higher level hub assembly - two view definitions */
#640 = PRODUCT('h1', 'hub assembly', $, (#220));
#650 = PRODUCT_DEFINITION_FORMATION('A','',#640);
#660 = PRODUCT_DEFINITION('dvh1', 'design view on hub assembly', #650, #230);
#670 = PRODUCT_DEFINITION('mvh1', 'maintenance view on hub assembly', #650, #240);
/* design life cycle 'as planned' assembly structure */
/* single occurrence of component (disc) defn in hub assembly defn */
#520 = NEXT_ASSEMBLY_USAGE_OCCURRENCE('d-1', 'single instance usage',
'du-1', #660, #400, $);
/* single occurrence of component (cap) defn in hub assembly defn */
#530 = NEXT_ASSEMBLY_USAGE_OCCURRENCE('c-1', 'single instance usage',
'cu-1', #660, #700, $);
/* maintenance life cycle planned disassembly structure */
/* single "phantom" hubcap subassembly occurrence in hub disassembly */
#560 = NEXT_ASSEMBLY_USAGE_OCCURRENCE('hc-1', 'single instance usage',
'hc-1', #670, #460, $);
/* single occurrence of component (disc) defn in hubcap sub-assembly */
#540 = NEXT_ASSEMBLY_USAGE_OCCURRENCE('d-1', 'single instance usage',
'du-1', #460, #410, $);
/* single occurrence of component (cap) defn in hubcap sub-assembly */
#550 = NEXT_ASSEMBLY_USAGE_OCCURRENCE('c-1', 'single instance usage',
'cu-1', #460, #710, $);
