Equation 3 · Ten Failure Modes That Define Production RAG
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Every index commits, at build time, to a unit of retrieval: a fixed-length passage, a paragraph, a sliding window. That commitment is made once, before any query exists, by whoever configured the ingestion pipeline. Chen and colleagues showed the choice is not neutral: indexing a corpus at the level of atomic propositions rather than fixed passages measurably improved both retrieval accuracy and downstream question answering, because a conventional passage boundary routinely separates a fact from the qualifying clause, the exception, or the date that gives it meaning [ 3 ] . The failure is retrieval-side as well as representation-side — if the true answer to a query spans two adjacent…
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Every index commits, at build time, to a unit of retrieval: a fixed-length passage, a paragraph, a sliding window. That commitment is made once, before any query exists, by whoever configured the ingestion pipeline. Chen and colleagues showed the choice is not neutral: indexing a corpus at the level of atomic propositions rather than fixed passages measurably improved both retrieval accuracy and downstream question answering, because a conventional passage boundary routinely separates a fact from the qualifying clause, the exception, or the date that gives it meaning [ 3 ] . The failure is retrieval-side as well as representation-side — if the true answer to a query spans two adjacent chunks, no top- k selection over those chunks can hand the generator both halves as one coherent unit, and overlap windows only reduce the frequency of the problem, not its existence, because the correct amount of overlap is a property of the query that has not been asked yet.
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