  We present Semi-Structured Explanations for COPA (COPA-SSE), a new
crowdsourced dataset of 9,747 semi-structured, English common sense
explanations for Choice of Plausible Alternatives (COPA) questions. The
explanations are formatted as a set of triple-like common sense statements with
ConceptNet relations but freely written concepts. This semi-structured format
strikes a balance between the high quality but low coverage of structured data
and the lower quality but high coverage of free-form crowdsourcing. Each
explanation also includes a set of human-given quality ratings. With their
familiar format, the explanations are geared towards commonsense reasoners
operating on knowledge graphs and serve as a starting point for ongoing work on
improving such systems. The dataset is available at
https://github.com/a-brassard/copa-sse.
