“Digital twin” usually means a model of the finished asset with sensors on it. Verian's 4D model is a different, more modest thing: a model of the build, coloured by what the site has reported, correct as of the data date and not a day later. This post explains the five steps between a row in a progress register and a colour on the model, and why there is a person in the middle of them.
Register → match → status → push → reforecast
- Register. Progress arrives as rows: a piping register from Excel, forty updates from Verian Mobile, a site diary. Each row has a quantity or a percentage, a date and a reporter.
- Match. Every row is matched to a model object (IFC) and a schedule activity. On the example register, 1,151 of 1,184 rows match without a question; the rest are held.
- Status. The status engine turns matched rows into one of four states per object: not yet, being built, built, behind its baseline. One meaning each; no fifth state.
- Push, with approval. Nothing reaches the schedule until the person with authority over that part of it approves the week's updates, together, with the checks already done.
- Reforecast. The approved progress moves the forecast dates. The reforecast is deterministic and shows its formula, so the planner can see why a date moved.
Matching a row to an object
The match is the unglamorous part and the part that decides whether the model can be trusted. A register row says spool SP-1188, Area A, 80 %. The matcher finds the IFC object carrying that tag, the activity that installs it, and checks that the row is consistent with both: that the support the spool sits on is reported as built, that the activity has started, that the quantity does not exceed what the register was supposed to cover.
| Register row | Matched to | Result |
|---|---|---|
| SP-1188 · Area A · 80 % | IFC object #40217 · A-1188 | Applied, pending approval |
| Tie-in TI-1212 · 100 % | IFC object #40355 · A-1212 | Held: finishes before its predecessor started |
| Bents 5–8 · 35 % | IFC objects #30118–30121 · A-1040 | Applied, pending approval |
| Spool SP-1190 · 60 % | no object with that tag | Held: asked the reporter |
Four states, one meaning each
A model that uses twelve colours tells you nothing at a glance. Verian uses four, and each has exactly one meaning. Not yet: no reported progress. Being built: started, not finished, as reported. Built: reported complete. Behind its baseline: the reported state is later than the baseline said it would be on this date. The fourth is the one people look for, and it is computed against the locked baseline, not against the forecast, so it cannot be moved by a reforecast.
Why the person is in the middle
It would be faster to colour the model straight from the register. It would also be wrong about once a week, and a model that is wrong once a week is a model nobody puts in front of a client. The construction manager approves the week's updates in one sitting, with the held rows already separated and the questions already asked. Then the model moves, the schedule moves, and every date carries a name.
Current beside scenario
Because the model is driven by the schedule, it can show two schedules at once: the current one and a recovery scenario, side by side, at the same date. The work that moves lights up with the difference in days. It is the fastest way we know to explain a recovery to someone who does not read Gantt charts, and it is the same scenario machinery the first post in this series used.
- A twin of the build, synchronised at the data date, not a twin of the asset.
- Every colour points back to a register row, an import and a date.
- Four states with one meaning each; behind-baseline is measured against the locked baseline.
- Nothing changes on the model without a person's approval.
- Reforecasts are deterministic and show their formula.