Tamino XQuery User Guide - Software AG Documentation

Text Retrieval
In the context of pattern matching, a word consists of a non-empty sequence of characters: for
example, a wildcard character (default: asterisk) matches zero or more characters in a word, so that
a single "*" represents a single word. If the search string contains more than one word, such as in
the expression tf:containsText($node, "word1 word2") then it is treated as
tf:containsAdjacentText($node, 1, "word1", "word2").
The following sections contain more information about searching with any of these special characters
and how to change the default setting:
■ The Maskcard Character
■ Wildcard Characters
■ The Escapecard Character
■ Customizing Special Character Settings
The Maskcard Character
The maskcard character, which by default is a question mark "?", stands for a single character in
a word. A pattern theat?? thus matches theatre as well as theater, but not theatrical since ??
only match ri and the rest (cal) is not matched.
Consider the following query:
let $text := text{"one two three four five six seven eight nine ten"}
return
(tf:containsText($text, "??"), tf:containsText($text, "t??"), tf:containsText($text, ↩
"two?three"))
The query returns a sequence of three items, each being a Boolean value that indicates whether
the specified pattern matches the contents of the text node in $text. Attempting to match the first
pattern ?? yields "false", since there are no numerals with only two letters. The second pattern t??
matches all three-letter numerals beginning with t, namely two and ten, so "true" is returned. The
last pattern fails again, although the pattern two?three seems to match the value "two three".
However, since pattern matching is always performed on the basis of a word, the match does not
succeed: the string "two three" is treated as two words delimited by the space character in between.
Note: Introducing the question mark as a maskcard character also has the effect that it is no
longer classified as a delimiter character in the default transliteration.
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