On run diversity in Evaluation as a Service

"Evaluation as a service" (EaaS) is a new methodology that enables community-wide evaluations and the construction of test collections on documents that cannot be distributed. The basic idea is that evaluation organizers provide a service API through which the evaluation task can be completed. However, this concept violates some of the premises of traditional pool-based collection building and thus calls into question the quality of the resulting test collection. In particular, the service API might restrict the diversity of runs that contribute to the pool: this might hamper innovation by researchers and lead to incomplete judgment pools that affect the reusability of the collection. This paper shows that the distinctiveness of the retrieval runs used to construct the first test collection built using EaaS, the TREC 2013 Microblog collection, is not substantially different from that of the TREC-8 ad hoc collection, a high-quality collection built using traditional pooling. Further analysis using the `leave out uniques' test suggests that pools from the Microblog 2013 collection are less complete than those from TREC-8, although both collections benefit from the presence of distinctive and effective manual runs. Although we cannot yet generalize to all EaaS implementations, our analyses reveal no obvious flaws in the test collection built using the methodology in the TREC 2013 Microblog track.