Editing Relevance (section)

=== Library and information science ===
{{Main|Relevance (information retrieval)}}
{{Recommender systems}}
This field has considered when documents (or document representations) retrieved from databases are relevant or non-relevant. Given a conception of relevance, two measures have been applied: [[Precision and recall]]:

Recall = ''a'' : (''a'' + ''c''), where
: ''a'' is the number of retrieved, relevant documents,
: ''c'' is the number of non-retrieved, relevant documents (sometimes termed "silence").
Recall is thus an expression of how exhaustive a search for documents is.

Precision = ''a'' : (''a'' + ''b''), where
: ''a'' is the number of retrieved, relevant documents,
: ''b'' is the number of retrieved, non-relevant documents (often termed "noise").

Precision is thus a measure of the amount of noise in document-retrieval.

Relevance itself has in the literature often been based on what is termed "the system's view" and "the user's view". Hjørland (2010) criticize these two views and defends a "subject knowledge view of relevance".