task_categories:sentence-similarity task_categories:feature-extraction task_categories:text-retrieval task_categories:question-answering task_categories:other task_ids:document-retrieval task_ids:open-domain-qa task_ids:closed-domain-qa multilinguality:monolingual language:de size_categories:10K<n<100K arxiv:2104.08663 region:us information retrieval ir documents retrieval passage retrieval beir benchmark qrel sts semantic search