Case Study

1
Case Study

• Oil Tanker Terminal Control System

2
Specification

• Tanker is the set of tankers
• Berth is the set of berths
• The given set is
• Tanker, Berth
• In any particular oil terminal there will be a
  certain set of berths available for tanker to use
• berths P Berth

3

• The definition below gives the response to an
  operation
• OTSResp okwaitmove-tanker
• known-tankernot-at-berth

4
State Data

• Declaration
• a queue of tankers waiting for berths,
• a record of which tanker occupies which berth
• The set of tankers that are either occupying
  berths or queuing for them

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Declaration for state data
Otcsys Waiting seq Tanker Docked Tanker ?
Berth Known P Tanker
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State Data

• Predicate
• A tanker cannot be both in the queue and in a
  berth
• The tanker queuing will all be different
• No tanker will be queuing unless all the berths
  are full
• Tankers occupying berths will all be different

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State Data
Otcsys waiting seq Tanker docked Tanker ?
Berth known P Tanker
ran waiting n dom docked Ø waiting (ran
waiting) waiting gt 0 ?ran docked berths ran
docked ? berths known ran waiting ? dom docked
8
Initializing state data
InitOtc Otcsys waiting lt gt docked Ø
In the initial state there are no tankers queuing
and all berths are free
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Operation tankers arriving(1)

• Only tankers not already queuing or docked can
  ask for permission to arrive.

Arrive0 ?Otcsys T? Tanker T? ? known
10
Operation tankers arriving(2)

• If there is a free berth, the tanker is allocated
  to it

ArriveNoQ Arrive0 B? Berth Res!
OTSResp ran docked ? berths Res! ok B? ?
berths \ ran docked docked docked ? T? ?
B? Waiting waiting
11
Operation tankers arriving(3)

• If there is no free berth, the tanker must be
  queued

ArriveQ Arrive0 Res! OTSResp ran
docked berths Res! wait B? ? berths \ ran
docked waiting waiting ltT?gt docked docked
ArriveOk ? ArriveQ ? ArriveNoQ
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Operation tankers leaving(1)

• A tanker can apply to leave if it is at berth.

Leave0 ?Otcsys T? Tanker T? ? dom docked
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Operation tankers leaving(2)

• If there is no queue, the berth is freed

LeaveNoQ Leave0 Res! OTSResp waiting
lt gt docked T? ? docked Waiting
waiting Res! ok
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Operation tankers leaving(3)

• If there is a queue, the operation must output
  the berth and the tanker next to occupy it, must
  update the docked function

LeaveQ Leave0 C! Tanker B! Berth Res!
OTSResp waiting ? lt gt C! head waiting B!
docked T? docked (T? ? docked) ? C! ?
B! waiting tail waiting Res! move-tanker
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Operation tankers leaving (4)
LeaveOk ? LeaveQ ? LeaveNoQ