Tetsuya Sakai, Sijie Tao, Nuo Chen, Yujing Li, Maria Maistro, Zhumin Chu, Nicola Ferro &ndash; Waseda University, Japan; University of Copenhagen, Denmark; Tsinghua University, P. R. C.; University of Padua, Italy
On the Ordering of Pooled Web Pages, Gold Assessments, and Bronze Assessments
The present study leverages a recent opportunity we had to create a new English web search test collection for the NTCIR-16 We Want Web (WWW-4) task, which concluded in June 2022. More specifically, through the test collection construction effort, we examined two factors that may affect the relevance assessments of depth-k pools, which in turn may affect the relative evaluation of different IR systems. The first factor is the document ordering strategy for the assessors, namely, prioritisation (PRI) and randomisation (RND). PRI is a method that has been used in NTCIR tasks for over a decade; it ranks the pooled documents by a kind of pseudorelevance for the assessors. The second factor is assessor type, i.e., Gold or Bronze. Gold assessors are the topic creators and therefore they “know” which documents are (highly) relevant and which are not; Bronze assessors are not the topic creators and may lack sufficient knowledge about the topics. We believe that our study is unique in that the authors of this paper served as the Gold assessors when creating the WWW-4 test collection, which enabled us to closely examine why Bronze assessments differ from the Gold ones. Our research questions examine assessor efficiency (RQ1), inter-assessor agreement (RQ2), system ranking similarity with different qrels files (RQ3), system ranking robustness to the choice of test topics (RQ4), and the reasons why Bronze assessors tend to be more liberal than Gold assessors (RQ5). The most remarkable of our results are as follows. Firstly, in the comparisons for RQ1 through RQ4, it turned out that what may matter more than the document ordering strategy (PRI vs. RND) and the assessor type (Gold vs. Bronze) is how well-motivated and/or well-trained the Bronze assessors are. Secondly, regarding RQ5, of the documents originally judged nonrelevant by the Gold assessors contrary to the Bronze assessors in our experiments, almost one half were truly relevant according to the Gold assessors’ own reconsiderations. This result suggests that even Gold assessors are far from perfect; budget permitting, it may be beneficial to hire highly-motivated Bronze assessors in addition to Gold assessors so that they can complement each other.
The WWW-4 task introduced a new English web corpus called Chuweb21, which was constructed based on the April 2021 block of Common Crawl dataset.⁹ [⁹ https://commoncrawl.org/2021/04/april-2021-crawl-archive-now-available/] Details of the corpus construction process can be found in the WWW-4 overview paper [38]. Chuweb21 contains 82,451,337 HTMLs or 1.69 TiB of compressed content; it is publicly available.¹⁰