  Fact-centric question answering (QA) often requires access to multiple,
heterogeneous, information sources. By jointly considering several sources like
a knowledge base (KB), a text collection, and tables from the web, QA systems
can enhance their answer coverage and confidence. However, existing QA
benchmarks are mostly constructed with a single source of knowledge in mind.
This limits capabilities of these benchmarks to fairly evaluate QA systems that
can tap into more than one information repository. To bridge this gap, we
release CompMix, a crowdsourced QA benchmark which naturally demands the
integration of a mixture of input sources. CompMix has a total of 9,410
questions, and features several complex intents like joins and temporal
conditions. Evaluation of a range of QA systems on CompMix highlights the need
for further research on leveraging information from heterogeneous sources.
