WSDM

We are delighted to welcome you to the proceedings volume of the Twelfth ACM International Conference onWeb Search and Data Mining (WSDM 2019), held in Melbourne, Australia on February 11-15, 2019. Now in its twelfth year, WSDMis a top tier conference in web-inspired research relating to search and data mining. Headline features of WSDM 2019 will include the sequence of very strong keynote presentations by Jaime Teevan, H. V. Jagadish, Rohit Prasad, Aleksandra Korolova, and Maarten de Rijke, and we thank them for their willingness to attend the conference and provide their insights.

As in previous years, there was a strong pool of research submissions, with 511 full-length papers received, a similar number compared to Los Angeles (2018) and Cambridge (2017), which had 514 and 505 submissions respectively. The submissions originated from 43 countries. Of the papers received, 84 were accepted and are included in these proceedings (the same number as were accepted in 2018), representing an acceptance rate of 16.4% (versus 16.1% in 2018) and within the range established through the previous eleven years (minimum 15.5%, maximum 22.3%). The final 84 papers are from 23 countries and span six continents, making WSDM a truly international forum.

In 2019 we continued the single-track model that is a hallmark of WSDM, with a mix of long-talk presentations and short-talk presentations, an approach that was introduced in 2012. Of the 84 accepted papers, 50 were assigned a five-minute talk, and 34 were assigned a longer fifteen-minute slot. All authors also had an opportunity to engage in detailed interactions during a 45-minute afternoon poster session held on the same day as their oral presentation. The selection between long-talk and short-talk presentation was made by the Program Chairs, based on whether the topic and content of the paper was better suited to large group presentation or to focused and interactive presentation, and was independent of the paper reviewing process. All accepted papers have equal standing in the proceedings.

The program committee worked hard to assess the submissions and provide feedback to help improve the papers. At least three program committee members reviewed each submission, together with a senior PC member who oversaw discussion amongst the reviewers and provided an overall recommendation. To discuss papers and ensure consistency across the entire decision process a PC meeting of available SPC members and the PC Chairs was held in Los Angeles on October 18th, with other SPC members participating remotely.

We acknowledge the tremendous work of the 208 members of the Program Committee (representing 27 countries), and in particular the efforts of the 65 Senior Program Committee members. They are the cornerstone of the high-quality program that has emerged in 2019. After discussion with past WSDM chairs and the WSDM Steering Committee, the reviewing model used in 2019 was a mix of single- and double-blind evaluation. Submissions were prepared using a doubleblind format, with no author information allowed (however authors were permitted to indicate the source of their data set and/or deployment environment, to avoid references to "major commercial search engines" as has occurred in the past). First-tier PC members had no access to author names or affiliations, allowing them to provide double-blind bias-free review. However, to more rigorously vet for conflict of interest (CoI) issues between authors and first-tier referees, SPC members could see both author names and author affiliations.

From the set of accepted papers, a number of candidates for best paper were passed to the Best Paper Chair, Arjen de Vries. All accepted papers that were nominated by both a PC member and the SPC member assigned to the paper as best paper were included in the candidates, as were any of the top 17 scoring papers (chosen by a score threshold) if they were additionally nominated by either a PC or SPC member. The Best Paper Chair then recruited further referees with minimal conflicts of interest with the candidate set, and coordinated the evaluation that then led to the Best Paper awards that were announced at the conference banquet at the National Gallery of Victoria.

The WSDM 2019 program had several tracks in addition to the main research paper sequence. These tracks were run independently, under the oversight of the General and PC Chairs. The tutorial chairs were Jeff Dalton and Claudia Hauff; they managed a selection process that evaluated the tutorial proposals, and accepted one full-day tutorial and six half-day tutorials.

Hideo Joho and Min Zhang were responsible for Workshop selection; their track received eight proposals, with five workshops accepted and one subsequently withdrawn, and four included in the program as half-day events on the final day of the conference. The WSDM Cup was also held on the last day. It consisted of winner' presentations and discussion in connection with data challenges based on resources provided by four of the sponsors, and was organized by Zhifeng Bao and Jianzhong Qi. The Doctoral Consortium Chairs were Laura Dietz and Carsten Eickhoff; their track received ten submissions, and accepted nine for inclusion in the program. The review focus in the Doctoral Consortium was on providing feedback to the students, and not merely accept/reject decisions.

The Industry Day program on the first day ofWSDM2019 was coordinated by Daria Sorokina and Jussi Karlgren. In an innovative step they made an open call for submissions, and accepted nine of the 18 proposals that resulted. Those talks will be recorded, and made available postconference for others to view.

Demonstrations were managed by Laurianne Sitbon and Paul Thomas. That track received 26 submissions and accepted 12 of them (46%). Each demo submission was reviewed by three reviewers; submissions with divergent reviews were then discussed to resolve conflicts.

We gratefully acknowledge the contributions made by these various Chairs and the other committee members listed over the next few pages. We are also indebted to our various supporters and sponsors; without them the conference would not have been possible. Additional thanks are owed to SIGIR for their generous student travel support.

ICMS Australasia provided expert assistance with the logistics of the event, and we thank them for their professional advice and guidance. We also benefited greatly from the support provided by the Melbourne Convention Bureau; and from the knowledge and skills of the many expert staff at the Melbourne Convention and Exhibition Center, the venue for WSDM 2019.

Finally, we are in debt to the authors and attendees, who are the ones who made this conference a success and have allowed WSDM to become a wonderful forum to advanceWeb research, and the premier ACM conference in the field. Our goal was to not only give you the opportunity to share ideas with other researchers and practitioners from around the world, but also to foster new research and innovation in this fascinating Web era. We trust that you enjoy the many WSDM 2019 conference activities, and also the other opportunities you are able to fit in during your visit to Melbourne, to Australia, and indeed, to the southern hemisphere.