Zone 3 Access: Four Rules and One Roster
Ashcombe Data Centre controls Zone 3 access with four written rules: (R1) a person may enter Zone 3 only while holding a valid Zone 2 endorsement; (R2) anyone whose safety certificate has expired is barred from Zone 3 regardless of any other clearance; (R3) a contractor may enter Zone 3 only if they hold a current Zone 3 endorsement and remain, at all times and within sight, accompanied by a permanent employee holding Zone 3 clearance; (R4) Zone 3 clearance may not be held by a person under an active disciplinary suspension. Today's roster: Priya, permanent, Zone 2 valid, Zone 3 clearance held, safety certificate expired two days ago. Tomas, contractor, Zone 2 valid, safety certificate valid, Zone 3 endorsement application still pending. Aisha, permanent, Zone 3 clearance held, safety certificate valid, Zone 2 endorsement lapsed last month with renewal booked for Friday. Daniel, contractor, Zone 2 valid, Zone 3 endorsement granted, safety certificate valid. No other Zone 3-cleared staff are on site. The duty manager must approve or refuse each person this morning.
1. Who, if anyone, may enter Zone 3 today? Give the rule-by-rule deduction for each person.
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Priya - refused. R1 satisfied (Zone 2 valid) and she holds Zone 3 clearance, but R2 is an overriding bar: her safety certificate expired two days ago. R2 says 'regardless of any other clearance', so nothing else she holds can cure it.
Aisha - refused. Safety certificate valid and Zone 3 clearance held, but R1 fails: her Zone 2 endorsement lapsed last month. A renewal booked for Friday is not a valid endorsement today; the rule turns on the state of the record, not on intent.
Daniel - refused. R1 satisfied, R2 satisfied, R3's first limb satisfied (endorsement granted). He fails the second limb: he must be accompanied at all times and within sight by a permanent employee holding Zone 3 clearance. The only two such employees on site are Priya (barred by R2) and Aisha (barred by R1). An escort who cannot lawfully be in Zone 3 cannot satisfy R3.
Tomas - refused, twice over. R1 and R2 satisfied, but R3 fails on both limbs: endorsement still pending, and no lawful escort exists.
R4 - never engaged. Nobody on the roster is under an active suspension. It is a live rule, simply not triggered; do not treat it as satisfied by default when recording the decision.
Answer: nobody enters Zone 3 today. The decisive feature is not any single person's defect but the escort requirement: both potential escorts are disqualified, by two different rules, so the roster fails structurally rather than individually.
2. The duty manager proposes to approve Daniel on his own because his endorsement has been granted. Identify the reasoning error, and the second error he would make if he added Priya as Daniel's escort.
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First error - necessary condition treated as sufficient. R3 is a conjunction: endorsement AND continuous escort. An endorsement is one limb of a two-limb test. Approving Daniel on the endorsement alone silently deletes the accompaniment requirement, which is the limb that actually manages physical risk in the room.
Second error - an unlawful escort. Naming Priya would add a second, more serious fault. R2 bars her from Zone 3 outright, so she cannot discharge an obligation that requires a person lawfully present. The rule is not 'a permanent employee is nearby'; it is 'a permanent employee holding Zone 3 clearance, within sight at all times'. A barred escort is worse than no escort, because it manufactures a paper trail that says the control was applied.
Both errors share a root cause: reading a multi-clause rule as a checklist of nice-to-haves rather than as an AND-gate. The correct habit is to restate the rule as a test - 'endorsement? yes/no. Escort available, cleared and unbarred? yes/no. Both yes → admit; otherwise refuse' - and to test the escort's own eligibility against R1, R2 and R4 before relying on them.
Note also the practical trap in 'within sight at all times': it survives only if the escort does not leave for a break, a call or a second task. Approval should carry that condition in writing.
3. Which single change admits the most people today, and can any single change admit all four? Justify with counts.
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Test each candidate fix by counting admissions, not by how easy it is.
- Renew Priya's safety certificate (a short online refresher, minutes not days): Priya admitted → she becomes a lawful escort → Daniel admitted as her accompanied contractor. 2 people. Tomas still lacks an endorsement; Aisha still lacks Zone 2.
- Expedite Aisha's Zone 2 renewal (booked for Friday): Aisha admitted → she can escort Daniel. 2 people. Priya still barred by R2.
- Expedite Tomas's Zone 3 endorsement: he would then satisfy R3's first limb but still has no lawful escort, since both escorts remain barred. 0 people. This is the counter-intuitive result and the one worth stating: the fix that looks most obviously relevant to the person blocked that day achieves nothing on its own.
Best single change: Priya's certificate - 2 admissions, and it is achievable today.
Can one change admit all four? No. The blocks are independent: Priya's expired certificate, Aisha's lapsed Zone 2, Tomas's missing endorsement. A single change addresses at most one of those, and Daniel's admission rides on Priya's or Aisha's.
Reaching three requires two changes - Priya's certificate and Tomas's endorsement - with Priya escorting both. Check the wording before relying on that: 'at all times and within sight' means she can supervise two contractors only if they stay together in her sight line. Four is impossible today without a third fix for Aisha.