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A question about part2

 
Greenhorn
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Can someone tell me what is equipment?
Thank you!
 
Ranch Hand
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An airplane.
 
Greenhorn
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Thank you Jun Hong!
 
Greenhorn
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Originally posted by Jun Hong:
An airplane.


Then how could explain the 1-1 relationship?
an airplane could only be used for a flight? It seems unrealistic.
Thanks
 
author and jackaroo
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Hi Dissip,
Welcome to JavaRanch.
I'll try and explain a way that this might work - you will have to decide for yourself whether this fits or not.
In the airline industry, they quite often change the type of plane for a given flight depending on the number of bookings. So even if you caught the same flight number every day between the same cities at the same time, you might get a different type of aircraft. For example a 747 holds roughly 400 passengers (it varies by 747 model number), whereas a DC-10 holds roughly 300 people - either might be used for the same route, depending on the number of passengers booked for a certain flight on a certain day.
Furthermore the seating types themselves can change on any given day (although this doesn't normally apply to the low cost airlines). So today's flight might have 9 first class seats, 30 business class seats, and 335 econonmy class seats. But tomorrow's flight on the same physical aircraft may have 6 first class seats, 20 business class seats, and 358 economy class seats - all dependant on what sort of bookings the airline has already taken and what their expected usage of the flights will be.
So, in a sense, each individual flight can be considered to have a unique aircraft.
Does this help?
Regards, Andrew
[ March 12, 2004: Message edited by: Andrew Monkhouse ]
 
dissip angler
Greenhorn
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Thank you very much, Andrew.
And what's your opinion about the 1-1 relationship between the segment and the flight?
As I think a segment is a part of the itinerary reservation. And a flight is a trip of an airplane (equipment) from one city to another at specific date and time.
So it is reasonable that every segment correspond to 1 flight. But how could a flight just correspond just 1 segment (reservation).
(Although I tried to interpret the segment and flight as some other things, such as segment: the route between 2 cities, flight a series of trips of an airplane from one city to another, it seems there's always a contradiction in the multiplicity of the relationships.)
Thank you again and looking forward for your reply.
 
Ranch Hand
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I have the same problem ��� 3 week ago that have this problem ����
I thinks that relation 1-->1 not is correct���

I need help us ��
 
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