implicit search

Implicit search filters perform two functions:

• Provide a concise way to search for literal strings
• Ensure that CQL 6.1 is back-compatible with CQL 6.0

When certain string filter (string filters) are followed by a string literal, the filter searches its value for an occurrence of that string literal. That is, for certain filters F,

    F "x" ≡ "x" in F

We call these filters implicit search filters.

The string literal (or quoted string) following F is called the implicit search parameter. Implicit search filters in CQL include all the following filters that query PGN tag values: site, event, player, white, black, date, eventdate.

Some Heijden database VI interface filter(hhdb filters) - every hhdb filter whose value is a string - are also implicit search filters. For example:

    player white "Kasparov" ≡ "Kasparov" in player white
    player 
    site "Zee" ≡ "Zee" in site
    event "Ch" ≡ "Ch" in event
    hhdb gbr "0134"
    hhdb composer "Adli"

Two other filters have a similar syntax to implicit search filters but are not true implicit search filters. The originalcomment filter is almost the same as an implicit search filter, but if the quoted string following originalcomment is a NAG ("numeric annotation glyph") then the argument is treated specially. The fen filter also can be followed by a single quoted string, but that string must be in a particular format denoting a FEN.