Using effectivity cutback

While defining a product managed with occurrence effectivity, the effectivity decisions evolve as the product content itself is developed. The design engineer makes decisions for effectivity ranges that reflect the implementation plan for when additional or replacement parts should be included in the bill of materials.

In general, there are many technical and logistical decisions that go into setting the date or unit range of the effectivity. To support this process, the engineer must understand the chain of effectivity for a given part. The engineer may choose to adjust the effectivity ranges when necessary. Over the life cycle of development and service of the product, customers using occurrence effectivity replace parts with other parts. As these changes are made, the historical chain of effectivity must remain consistent.

When a new occurrence of a part is specified as a replacement for an existing occurrence in a structure, the effectivity of the replaced part should be reduced (cut back) so that it does not overlap with the effectivity of the replacing part.

When a part with occurrence effectivity is replaced and cut back, prior generations that were replaced by the cutback part should also be considered for cutback, if the range of the newest replacement overlaps effectivity.

Note

Effectivity cutback is only supported with unit effectivity, not with date effectivity.

The following actions are supported by effectivity cutback:

• Replacing N parts with M replacements and updating ranges of effectivity. The historical chain of effectivity retains the N:M relationship, in case a future cutback operation needs to fully span the content of a link in the chain to cut it back.

• Validating prior replacements in the history of effectivity and updating accordingly.

• Enabling efficient updates to effectivity ranges after a replacement.

The following example shows how effectivity cutback occurs when an engineer modifies an assembly that is managed with occurrence effectivity.

1. The engineer specifies replacement parts P21, P22, and P23 for parts P11 and P12 with a unit range of 10-up.

The system adds the occurrences P21, P22, and P23 effective unit 10-up The effectivity of P11 and P12 is cut back to the portion of the range not set on the replacements, namely units 1-9.

2. The engineer indicates parts P31,P32, and P33 are specified as replacements to P21, P22, and P23 for a range starting at unit 5.

The system determines from the chain of effectivity and replacements that P21, P22, and P23 are replacements. The full range of effectivity is overlapped, so P21, P22, and P23 are no longer in effect. The span of replacement is complete, so the parts previously replaced are considered and P11 and P12 are cut back accordingly to 1-4.

3. The engineer specifies P42 as a replacement for P32 for a range within the span of effectivity of P32.

P42 is effective for the range specified (units 20-30) and the replaced occurrence split to 5-19, and 31-up.

4. The engineer adjusts the effectivity range of P42 to units 22-32.

The effectivity of P42 is updated to the new range.

5. A reviewer or the engineer validates the effectivity chain of P42.

The system evaluates the effectivity of P42 against the parts it replaced or is replaced by. It identifies:

A gap Unit 20,21 does not include replaced (P32) or replacing (P42) parts.

An overlap Units 31 and 32 include both replaced (P32) and replacing (P42) parts.

6. The engineer replaces a part where only a portion of the historical replacement chain is changing.

While a cutback of P33 by replacing part P43 is unambiguous, there is not an unambiguous action to take on P11 and P12 because P33 is only a subset of the historical chain: (P11,P12):(P21, P22, P23):(P31, P32, P33)

After replacing an occurrence and performing a cutback of the replaced part, the effectivity range of a part can be adjusted. If the new range overlaps with the effectivity of any parts in the historical chain of effectivity, the system issues a warning.

The following table shows how effectivity cutback occurs in this scenario.

Step	Task	Part P11	Part P12	Part P21	Part P22	Part P31	Part P32	Part P33	Part P42	Part P43
1	Initial state	1-up	1-up
2	Replace P11 & P12 with P21, P22,P23 at unit 10	1-9	1-9	10-up	10-up
3	Replace P21, P22, P23 with P31, P32, P33 at unit 5	1-4	1-4			5-up	5-up	5-up
4	Replace P32 with P42 for units 20-30	1-4	1-4			5-up	5-up	5-up	20-30
5	Adjust effectivity of P42 to units 22- 32						Warning		22-32
6	Replace P33 with P43 for units 3- 7	Error	Error					8-up		3-7

When a link in a chain of occurrence effectivities is completely overlapped (that is, a complete cutback is made of its entire range) it is logically removed from the structure. The system informs the user there is no effectivity for that occurrence. A logically removed occurrence can be removed from the structure and removed from historical chains of effectivity used for evaluation of future cutback operations. In this situation, the change history is the only way to know the part ever existed in the structure.