Effectivity Dates and Revisions

Every line in a structure carries effectivity dates — the window during which that component belongs to that parent. This is deliberately not optional.

The question effectivity answers

A structure without dates can only tell you what a product is made of now. The question that actually gets asked is what it was made of in March — and it is asked in the worst circumstances, usually after a recall, a customer complaint or a supplier defect.

If a supplier tells you a batch of components shipped between two dates was defective, you need to know which of your products used that component during that window and which customers received them. Without dated structures, the honest answer is that you cannot tell, and the practical answer is to recall everything.

Changing a structure

You do not edit a structure line to change a component. You end the effectivity of the old line and start a new one from the changeover date. Both remain, so both the old and the new answer are available depending on the date you ask about.

Revisions

A revision groups a set of lines as a named version. Effectivity dates say when something applied; revisions say which design it belonged to. Use revisions where your engineering process already thinks in versions, and rely on dates for the chronological question.

Planning a changeover

Because effectivity is dated, a future change can be entered in advance. Set the new line to start on the changeover date and end the old one the day before, and the system builds correctly on the day without anyone remembering to make the edit at midnight.

Check remaining stock of the outgoing component when planning the date — a changeover that strands inventory is an expensive way to be tidy.

Explosions are dated too

When you explode a structure, the date matters. Exploding for a works order due next month uses the structure effective then, not the one effective today. If an explosion looks wrong, check the date you asked about before checking the structure.