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SECTION 28 / 28
Keep and flag inconsistent source records
REAL COURSE DATA · SORT, GROUP AND VERIFY
Cross-check two historical timetable views
Follow the selected procedure. Change a field, tie rule or weekday and explain why the result changes.
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Predict the next change. Keep track of which list level, field and position convention the procedure uses.
The lecture stresses that train and station cards should agree after accounting for journey-day offsets. Actual supplied cards also provide a useful sanity-check example: 02245’s train-wise card lists Tue, Wed, Sat, Sun, while the Bhubaneswar station card lists Tue, Wed, Fri, Sat, Sun. Friday is extra in the station view.
We preserve that discrepancy instead of silently inventing a correction. The direct-route explorer uses the verified train-wise card weekdays and labels its source. The separate cross-view activity reports the conflicting station entry. Resolving which view is authoritative would require more source evidence.
Do not confuse this disagreement with a valid day shift such as 02201 arriving the day after departure, or with 12270’s midnight arrival/departure split. First define the meaning of each field, then compare like events. Data validation is part of computational thinking, not a reason to hide inconvenient examples.
Try it yourself
Should you add Friday to the train card just to make the views agree?
Show explained answer
No. Keep the original values and flag the unresolved conflict unless an authoritative correction is available.
Try it yourself
Why is a one-day difference sometimes valid?
Show explained answer
The station can be reached on Journey Day 2, so its event weekday is one day after origin departure.
Try it yourself
What source does the route explorer use for operating days?
Show explained answer
The ten visually verified train-wise cards, with explicitly derived station event days.