BARNHART, BELOBABA, AND ODONI
Operations Research in the Air Transport Industry
what has come to be known as “virtual nesting”
(Smith et al. 1992), an assignment process that maps
each itinerary/fare type to a hidden or “virtual” value
class within the airline’s own reservations system. For
an itinerary/fare assigned to a given virtual class,
the seat availability on a given flight leg is established
by the booking limit for that virtual class. Initial
implementations of virtual nesting were based on
total itinerary fare values, giving preference to longerhaul
connecting passengers with higher total fares.
The shortcoming of this “greedy” approach was that
it did not address the need under certain circumstances
to give preference to two “local” passengers
instead of taking the connecting passenger.
OR models have been instrumental in the subsequent
development of O-D control strategies that
allowed airlines to manage seat inventories on
the basis of the network revenue value of each
itinerary/fare combination. Network revenue value can
be defined as the total itinerary fare (ticket value)
minus the revenue displacement that might occur on
connecting flight legs if the passenger’s request for
a multiple-leg itinerary is accepted. For example, the
network revenue value of an $800 total fare on the
first leg of a connecting itinerary must be reduced by
$300 if acceptance of this passenger would result in
displacement of $300 in total network revenue on the
second flight leg. The displacement cost associated
with the last (lowest valued) available seat on a given
flight leg is its marginal value to the total network
revenue—the amount by which the total network revenue
would decrease if we were to “remove” (or sell)
one seat on the flight leg. If the flight leg consistently
has empty seats, the marginal network value of its
last seat would be zero. In the more realistic situation
where the flight leg has a significant probability
of being full and it carries both local and connecting
passengers, determining the impact on total network
revenues of removing a seat can require substantially
more complicated analysis, including network optimization
models.
Various network optimization and heuristic algorithms
have been applied to the problem of determining
the network revenue value contribution of
each O-D itinerary and fare product (or ODIF). As
described in Belobaba (1998), several large airlines
make use of leg-based EMSR values to approximate
the network revenue value associated with a given
connecting itinerary/fare combination. Because these
approaches do not make use of any formal network
optimization models, they are referred to as “legbased
heuristic” models for estimating network revenue
displacement.
The majority of published works devoted to the
O-D seat inventory control problem have proposed
mathematical programming approaches to determine
optimal seat allocations for every ODIF over a network
of connecting flight legs (see, for example,
Glover et al. 1982, Dror et al. 1988, and Curry 1990).
Williamson’s (1992) doctoral thesis provides a comprehensive
review of the literature relevant to the application
of mathematical programming and network flow
models to the O-D seat inventory control problem.
More recently, there have been new works proposing
more sophisticated network models. For example,
Bratu (1998) developed a “probabilistic network
convergence” algorithm for estimating the marginal
network value of the last available seat on each leg
in an airline network. Talluri and van Ryzin (1999a)
propose a randomized linear programming method,
while stochastic dynamic programming is also being
pursued as an alternative algorithm for determining
the marginal network value of a range of remaining
seats on each flight leg to account for changes to the
marginal value as bookings are accepted.
Given an estimate of down-line revenue displacement
it is possible to map ODIFs to virtual classes
based on their estimated network revenue value. Displacement
adjusted virtual nesting (DAVN) increases
availability to connecting passengers, while adjustment
for down-line displacement of revenues ensures
that two local passengers (with a higher total revenue)
will receive preference when two connecting flights
are expected to be heavily booked.
The estimated marginal network revenue of the
lowest-valued available seat on a flight leg can also
be used in a much simpler inventory control mechanism
based on bid price controls. At the time of an
ODIF request for seat availability, the ODIF fare is
evaluated against the sum of the leg bid prices over
the itinerary being requested. As was the case for estimates
of revenue displacement associated with connecting
passengers, leg bid prices can similarly be
BARNHART, BELOBABA, AND ODONIOperations Research in the Air Transport Industrywhat has come to be known as “virtual nesting”(Smith et al. 1992), an assignment process that mapseach itinerary/fare type to a hidden or “virtual” valueclass within the airline’s own reservations system. Foran itinerary/fare assigned to a given virtual class,the seat availability on a given flight leg is establishedby the booking limit for that virtual class. Initialimplementations of virtual nesting were based ontotal itinerary fare values, giving preference to longerhaulconnecting passengers with higher total fares.The shortcoming of this “greedy” approach was thatit did not address the need under certain circumstancesto give preference to two “local” passengersinstead of taking the connecting passenger.OR models have been instrumental in the subsequentdevelopment of O-D control strategies thatallowed airlines to manage seat inventories onthe basis of the network revenue value of eachitinerary/fare combination. Network revenue value canbe defined as the total itinerary fare (ticket value)minus the revenue displacement that might occur onconnecting flight legs if the passenger’s request fora multiple-leg itinerary is accepted. For example, thenetwork revenue value of an $800 total fare on thefirst leg of a connecting itinerary must be reduced by$300 if acceptance of this passenger would result indisplacement of $300 in total network revenue on thesecond flight leg. The displacement cost associatedwith the last (lowest valued) available seat on a givenflight leg is its marginal value to the total networkrevenue—the amount by which the total network revenuewould decrease if we were to “remove” (or sell)one seat on the flight leg. If the flight leg consistentlyhas empty seats, the marginal network value of itslast seat would be zero. In the more realistic situationwhere the flight leg has a significant probabilityof being full and it carries both local and connectingpassengers, determining the impact on total networkrevenues of removing a seat can require substantiallymore complicated analysis, including network optimizationmodels.Various network optimization and heuristic algorithmshave been applied to the problem of determiningthe network revenue value contribution ofeach O-D itinerary and fare product (or ODIF). Asdescribed in Belobaba (1998), several large airlinesmake use of leg-based EMSR values to approximatethe network revenue value associated with a givenconnecting itinerary/fare combination. Because theseapproaches do not make use of any formal networkoptimization models, they are referred to as “legbasedheuristic” models for estimating network revenuedisplacement.The majority of published works devoted to theO-D seat inventory control problem have proposedวิธีการเขียนโปรแกรมทางคณิตศาสตร์เพื่อกำหนดการปันส่วนที่นั่งที่ดีที่สุดสำหรับ ODIF ทุกเครือข่ายการเชื่อมต่อเที่ยวบินขา (ดู เช่นโกลเวอร์ et al. 1982, Dror et al. 1988 กแกงปี 1990)วิทยานิพนธ์พัฒนบริหารของ Williamson (1992) ให้ครอบคลุมทบทวนวรรณกรรมที่เกี่ยวข้องกับแอพลิเคชันการเขียนโปรแกรมคณิตศาสตร์และกระแสเครือข่ายรูปแบบปัญหาการควบคุมสินค้าคงคลังนั่ง O-Dเมื่อเร็ว ๆ นี้ มีการทำงานใหม่ที่เสนอรูปแบบเครือข่ายที่ซับซ้อนมากขึ้น ตัวอย่างประตูน้ำ (1998) พัฒนา "probabilistic เครือข่ายบรรจบกัน"อัลกอริทึมสำหรับการประมาณการกำไรค่านั่งสุดท้ายว่างบนขาแต่ละเครือข่ายในเครือข่ายสายการบิน Talluri และ van Ryzin (1999a)เสนอ randomized เส้นเขียนโปรแกรมวิธีการในขณะที่ยังมีการเขียนโปรแกรมแบบสโทแคสติกติดตามเป็นอัลกอริทึมอื่นสำหรับการกำหนดค่าของเครือข่ายต่ำของช่วงของส่วนที่เหลือที่นั่งในแต่ละขาบินการเปลี่ยนแปลงกำไรค่าที่รับจองกำหนดประมาณการรายได้ลงสายแทนจำเป็นต้องแม็ป ODIFs เรียนเสมือนตามค่ารายได้ของเครือข่ายโดยประมาณ ปริมาณกระบอกสูบการปรับปรุงเสมือนซ้อน (DAVN) เพิ่มขึ้นพร้อมการเชื่อมต่อผู้โดยสาร ขณะปรับปรุงสำหรับการย้ายรายได้ลงสายใจผู้โดยสารภายในเครื่องที่สอง (มีรายได้รวมสูงขึ้น)จะได้รับการตั้งค่าเมื่อสองการเชื่อมต่อเที่ยวบินare expected to be heavily booked.The estimated marginal network revenue of thelowest-valued available seat on a flight leg can alsobe used in a much simpler inventory control mechanismbased on bid price controls. At the time of anODIF request for seat availability, the ODIF fare isevaluated against the sum of the leg bid prices overthe itinerary being requested. As was the case for estimatesof revenue displacement associated with connectingpassengers, leg bid prices can similarly be
การแปล กรุณารอสักครู่..