The site filter takes a single argument which must be a quoted string. It is true if the argument string is a substring of the Site field of the game.
    site "Open"
An site filter may also be included as a CQL parameter, in addition to be used as an ordinary filter. For example,
    cql (input i.pgn site "Freiburg")
    countsquares 4 10 q
The site filter is used in the sample file gameinfo.cql .