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In plain terms: Most software can tell you what a ship is supposed to be today. Almost none can tell you how it got that way and what changed. In repair work, the second question is the expensive one.

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Two different clocks

Every vessel is really running two clocks at once.

The State Clock

Answers “what does the ship consist of right now?” The current model, the current bill of material, the structure as it stands. CAD and maintenance systems handle this clock reasonably well, as long as somebody keeps them updated.

The Event Clock

Answers “how did it get this way?” Which drawing established this structure, what the last survey found, which repair replaced what, who approved the change, what evidence supported it. Almost no system handles this clock at all.

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Why the second clock matters more in repair

For a new build, the state clock is nearly enough. The ship is being created, everyone involved was there, and the design intent is fresh. For a vessel that has been in service for 20 years, the state clock is the part you cannot trust. Nobody kept it updated. The drawings describe the ship as delivered, the CAD file describes some moment in between, and the steel describes today. The state clock has quietly gone wrong, and there is no way to tell where without the event clock. That is why the questions that actually come up in repair planning are event-clock questions:
  • “Was this section renewed in the last availability, or is that plate original?”
  • “The scan disagrees with the drawing here. Which one is more recent, and which one was measured?”
  • “This structure was accepted under the previous rule version. Does the update change it?”
  • “Why was this repair done this way last time, and did it hold?”
None of those can be answered from a snapshot of current state. They need the history of how the state came to be.

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Reconstruction needs both clocks

This is also why a reconstructed model cannot be just geometry. If reconstruction produced only a state, you would have a ship-shaped file with no way to tell which parts came from a clear drawing, which came from a contradiction between two sheets, and which are still open questions. Every part would look equally certain, and none of it would be checkable. So Forge carries the event clock alongside the geometry from the very beginning. Every reconstructed component keeps the sheet it came from, the interpretation applied, the conflicts encountered, and its current evidence state. The at the core of the system records the reasoning chain, not just the result.

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What this buys you

Because the event clock is preserved, the model can answer questions a static model cannot: That is the whole idea in one sentence. The rest of the Concepts section unpacks how Forge makes it work in practice:

From Drawings to a 3D Model

How 2D sheets become bounded geometry with the gaps left visible.

Sources vs. Decisions

The two kinds of things Forge handles, and why the distinction matters.

How a Decision Gets Made

A worked example, step by step, from a drydock question to a signed decision.

How CAD Becomes Engineering Evidence

How a model becomes a traceable measurement and a reviewable claim.