There is a traditional narrative within information studies regarding precision and recall measures. Precision and recall have been the most commonly used retrieval metrics and are the basis for more complicated and accurate information retrieval evaluations. Relevance, which is the criterion by which both recall and precision are judged, is subject to user interpretation and is context dependent. Although the determination of precision is straightforward, important ambiguities are involved when considering recall. Search evaluation metrics can be parsed into structural components. The interaction of the component parts can be clarified by the application of ontological distinctions. Possibly relevant items not retrieved are most usefully viewed as conceptually dependent parts. Positioned as the denominator of the recall measure, these parts function analogically and are supplemental in character. Although difficult to accurately determine, the recall denominator performs a useful role in the assessment of indexed data structures and other collection types.
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