The query also has some feature values that aren’t topical, such as the update
count feature. Of course, this doesn’t mean that the query has been updated. The
value of this feature indicates how important document updates are to relevance
for this query. For instance, if the query was “today’s weather in london”, we would
prefer documents that are updatedfrequently, since a document that isn’t updated
at least daily is unlikely to say anything interesting about today’s weather. This
query should have a high value for the update count feature. By contrast, a document
that never changed could be very relevant for the query “full text of moby
dick”. This query could have a low feature value for update count.