Defined in file entrez2.asn C++ class: CEntrez2_boolean_element Entrez2-boolean-element ::= CHOICE { str VisibleString , -- unparsed query string op Entrez2-operator , -- logical operator term Entrez2-boolean-term , -- fielded term ids Entrez2-id-list , -- list of UIDs - returns history key in reply key VisibleString } -- history key for uploaded UID list or other query