  On-the-fly retrieval of relevant knowledge has proven an essential element of
reliable systems for tasks such as open-domain question answering and fact
verification. However, because retrieval systems are not perfect, generation
models are required to generate outputs given partially or entirely irrelevant
passages. This can cause over- or under-reliance on context, and result in
problems in the generated output such as hallucinations. To alleviate these
problems, we propose FILCO, a method that improves the quality of the context
provided to the generator by (1) identifying useful context based on lexical
and information-theoretic approaches, and (2) training context filtering models
that can filter retrieved contexts at test time. We experiment on six
knowledge-intensive tasks with FLAN-T5 and LLaMa2, and demonstrate that our
method outperforms existing approaches on extractive question answering (QA),
complex multi-hop and long-form QA, fact verification, and dialog generation
tasks. FILCO effectively improves the quality of context, whether or not it
supports the canonical output.
