Data structures and meaning
Valid-time and recorded-time model
Bitemporal data: when a fact was true (valid time) versus when we learned it (record time), modeled explicitly.
ddn@1New DDN source
Why use it?
Most "history" tables answer only one of those questions; the diagram keeps both honest.
When it helps
Designing audit trails, corrections, or any as-of reporting.
How to read it
- Each fact carries two clocks; reads pick a point on each.
- A correction adds a row — it never edits the past in place.
What you need
- The facts that change
- Both time dimensions per fact
- The as-of questions to answer
Things to check
- Do not overwrite a fact when you mean to correct it.
- Do not confuse "when it happened" with "when it was entered".
Scope of this diagram
Model documentation; no temporal query evaluation.
Work with the converted example
- Open the viewer and select
diagram. Inspect the rendered view and its source. - Open the designer. Keep the selected profile and inspect its legal palette and property controls.
- Change one displayed title or an appropriate data value. Apply the edit and check the resulting diagram.
- Run the verifier and review its diagnostics before moving complete content into review.
- Download your edited DDN source to retain the change.
The example uses the indentation-based ddn-next-1 dialect. The language guide explains reusable definitions, dotted data rows and explicit property blocks.