Specify a search
specify_search(date, query, databases, fields)
The date that the search is conducted.
The query used in the search (as specified using the
functions for queries, e.g.
The databases that were searched, as a named list of vectors, where each vector's name is the name of the interface used to access the databases in the vector.
The fields in which the query terms were searched.
mbf_search object with the search specifications.