by Djoerd Hiemstra and Marie-Francine Moens
The 43rd European Conference on Information Retrieval, ECIR 2021, was supposed to take place as an in-person conference in Lucca, Italy. Due to the COVID-19 pandemic, ECIR 2021 was held entirely online from March 28 to April 1, 2021. The conference programme contained full paper presentations, poster presentations, system demonstrations, eight tutorials, five workshops, an industry event, a doctoral consortium, a reproducibility track, a panel on open access publishing and several online social events.
For this special issue, we asked the authors of eight of the ECIR 2021 full apers that had the best reviewing scores to submit an extended version of their paper. This led to five papers that are published in this special issue of the Information Retrieval Journal. The extended papers contain at least 30% new content. Examples of extensions are enhancements that improve the techniques described in the ECIR 2021 paper; as well as tests on additional datasets that reveal behaviors that differ from the originally published claims and that provide further insights into the methods being described. Among the papers in this special issue are extensions of two papers that received an award at ECIR 2021.