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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Booking.com WSDM WebTour 2021 Challenge</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Dmitri Goldenberg</string-name>
          <email>dima.goldenberg@booking.com</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Sarai Mizrachi</string-name>
          <email>sarai.mizrachi@booking.com</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Kostia Kofman</string-name>
          <email>kostia.kofman@booking.com</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Maayan Kafry</string-name>
          <email>maayan.kafry@booking.com</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Pavel Levin</string-name>
          <email>pavel.levin@booking.com</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Guy Nadav</string-name>
          <email>guy.nadav@booking.com</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Booking.com</institution>
          ,
          <addr-line>Amsterdam</addr-line>
          ,
          <country country="NL">Netherlands</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Booking.com</institution>
          ,
          <addr-line>Tel Aviv</addr-line>
          ,
          <country country="IL">Israel</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2021</year>
      </pub-date>
      <fpage>21</fpage>
      <lpage>22</lpage>
      <abstract>
        <p>The ACM WSDM WebTour 2021 Challenge focuses on a multidestinations trip planning problem, which is a popular scenario in the travel domain. The goal of the challenge is to make the best recommendation of an additional trip destination. To encourage research on this field, Booking.com provided a unique dataset based on millions of real anonymized bookings. More than 800 participants have signed up for the contest. Best performing team achieved Accuracy @ 4 of 0.5939, using a blend of Transformers, GRUs, and feed-forward multi-layer perceptron. Additional leading teams implemented advanced state-of-the-art solutions to tackle the problem.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>CCS CONCEPTS</title>
      <p>• Information systems → Personalization; Recommender
systems.</p>
    </sec>
    <sec id="sec-2">
      <title>PROBLEM DESCRIPTION</title>
      <p>Booking.com’s mission is to make it easier for everyone to
experience the world. By investing in the technology that helps take the
friction out of travel, Booking.com seamlessly connects millions of
travelers with memorable experiences, a range of transport options,
and incredible places to stay.</p>
      <p>
        Many of the travelers go on trips that include more than one
destination. For instance, a user from the US could fly to Amsterdam
for 5 nights, then spend 2 nights in Brussels, 3 in Paris, and 1 in
Amsterdam again before heading back home. In this scenario, the
users are ofered personalized recommendations [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ] for extending
their trip immediately when they make their booking, as shown in
ifgure 1.
      </p>
      <p>
        The goal of this challenge is to use a dataset based on millions
of real anonymized accommodation reservations to come up with
a strategy for making the best recommendation for their next
destination [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ]. Booking.com releases this unique dataset to encourage
the research on sequential recommendation problems [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ]. The
challenge is part of the WebTour 2021 ACM WSDM workshop [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ] on
web tourism that will be held at the 14th ACM international 2021
WSDM Conference.
Column
user_id
checkin
checkout
afiliate_id
device_class
booker_country
hotel_country
city_id
utrip_id
      </p>
      <sec id="sec-2-1">
        <title>Description</title>
        <sec id="sec-2-1-1">
          <title>User ID</title>
          <p>Reservation check-in date
Reservation check-out date
An anonymized ID of afiliate channel
where the booker came from (e.g. direct,
3rd party referrals, paid search engine, etc.)
desktop/mobile
Country from which the reservation was
made (anonymized)
Country of the hotel (anonymized)
city_id of the hotel’s city (anonymized)
trip ID (a group of multi-destinations
bookings within the same trip)
2</p>
        </sec>
      </sec>
    </sec>
    <sec id="sec-3">
      <title>DATASET</title>
      <p>The dataset consists of over a million anonymized hotel
reservations, based on real data, is available on the challenge website1
and described in table 1. Each reservation is a part of a customer’s
trip (identified by utrip_id), which includes at least four
consecutive reservations. There are 0 or more days between check-out
and check-in dates of two consecutive reservations. The evaluation
dataset is constructed similarly. However, the city_id of the final
reservation of each trip is concealed and requires a prediction.
1https://www.bookingchallenge.com/</p>
      <p>Test set release
teams registration deadline</p>
      <sec id="sec-3-1">
        <title>Challenge closes</title>
        <p>results submission deadline
Announcement on the winners
Paper submission deadline
Paper notifications
Camera ready submissions</p>
      </sec>
      <sec id="sec-3-2">
        <title>Workshop day</title>
        <p>3
4</p>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>CHALLENGE TIMELINE</title>
      <p>Key dates of the challenge are listed in table 2.</p>
    </sec>
    <sec id="sec-5">
      <title>SUBMISSION GUIDELINES</title>
      <p>The teams are expected to submit their top four cities predictions
per each trip on the test set until January 28th 2021. The submission
will be done in a csv file named submission.csv in the following
format described in table 3:
utrip_id represents each unique trip in the test, and the rest of
the columns represent the city_id of the top four predicted cities.
The top 10 teams will be invited to submit short papers (up to 4
pages + references in ACM sigconf format2). The papers will include
the team and the authors names, an abstract, a text describing the
method and the achieved score, and a link to their code repository
and refer to the Booking.com challenge in the following format:
Dmitri Goldenberg, Kostia Kofman, Pavel Levin, Sarai
Mizrachi, Maayan Kafry, and Guy Nadav. 2021. Booking.com
WebTour 2021 Challenge. http://www.bookingchallenge.com
, In ACM WSDM Workshop on Web Tourism (WSDM WebTour’21),
March 12th, 2021, Jerusalem, Israel.</p>
      <p>Selected papers are expected to present their work in the
workshop (in a virtual format). The submitted papers will be evaluated
based on their clarity, novelty, and results presentation. Please
contact wsdmchallenge@booking.com for any questions.
5</p>
    </sec>
    <sec id="sec-6">
      <title>EVALUATION CRITERIA</title>
      <p>The goal of the challenge is to predict (and recommend) the final
city (city_id) of each trip (utrip_id). The quality of the predictions
is evaluated based on the top four recommended cities for each trip</p>
      <sec id="sec-6-1">
        <title>Team Accuracy @ 4 1 2</title>
      </sec>
      <sec id="sec-6-2">
        <title>NVIDIA RAPIDS.AI</title>
      </sec>
      <sec id="sec-6-3">
        <title>Synerise AI</title>
      </sec>
      <sec id="sec-6-4">
        <title>TEAM DASOU</title>
        <p>mbaigorria</p>
        <p>aprec
hakubishin3 &amp; u++ &amp; yu-y4</p>
        <p>testing
Alexander Makeev</p>
        <p>YiNet
Marlesson - MARS-Gym
by using Top-4 Accuracy metric (4 representing the four suggestion
slots at Booking.com website). When the true city is one of the top
4 suggestions (regardless of the order), it is considered correct.
6</p>
      </sec>
    </sec>
    <sec id="sec-7">
      <title>PRIZES</title>
      <p>To encourage research contributions, the top three performing
teams will receive Booking.com Travel Credits. The best paper
team will receive an additional prize. Paper submission and virtual
participation at the workshop are mandatory in order to be eligible
for a prize.
7</p>
    </sec>
    <sec id="sec-8">
      <title>RESULTS</title>
      <p>820 participants have signed up for the challenge. After two months
of a contest, 97 of them performed a final submission, grouped in
40 competing teams. Top 10 performing teams are listed in table 4.
The best performing team achieved Accuracy @ 4 of 0.5939,
implementing a blend of 3 diferent neural network architectures, using
Transformers, GRUs, and feed-forward MLP. Other solutions relied
on Eficient Manifold Density Estimator, LSTM networks, Attention
mechanisms, Lambdarank, and further state-of-the-art methods.
The teams have submitted short papers and code repositories with
a detailed description of their solution methodology.</p>
    </sec>
  </body>
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