cql-query ::= cql-query boolean search-clause | search-clause boolean ::= "and" | "or" | "not" | prox search-clause ::= "(" cql-query ")" | [ qualifier relation ] term relation ::= base-relation { "/" relation-modifier } base-relation ::= numeric-relation | "exact" | "all" | "any" relation-modifier ::= "relevant" | "fuzzy" | "stem" numeric-relation ::= "<" | ">" | "<=" | ">=" | "<>" | "=" prox ::= "prox" [ "/" prox-parameters ] prox-parameters ::= [ numeric-relation ] "/" [ distance ] "/" [ unit ] "/" ordering | [ numeric-relation ] "/" [ distance ] "/" unit | [ numeric-relation ] "/" distance | numeric-relation unit ::= "word" | "sentence" | "paragraph" | "element" ordering ::= "ordered" | "unordered" distance ::= non-negative-integer qualifier ::= [ qualifier-prefix "." ] qualifier-name qualifier-prefix ::= identifier qualifier-name ::= identifier identifer ::= string term ::= string | ""string"" string ::= a character string