Searching using Regular Expressions
When searching for word forms and annotation values, it is possible to
employ wildcards as placeholders for a variety of characters, using
Regular Expression syntax (see e.g.
http://www.regular-expressions.info/ for detailed information).1
To search for wildcards use slashes instead of quotation marks to
surround your search term. For example, you can use the period (
to replace any single character:
This finds word forms such as "cat", "can", "car", "cap" etc. It is also
possible to make characters optional by following them with a question
?). The following example finds cases of "car" and "cart",
since the "t" is optional:
It is also possible to specify an arbitrary number of repetitions, with
an asterisk (
*) signifying zero or more occurrences and a plus
+) signifying at least one occurrence. For example, the first query
below finds "o", "of", and "off" (since the asterisk means zero or more
times the preceding "f"), while the second finds "of" and "off", since
at least one "f" must be found:
It is possible to combine these operators with the period operator to mean any number of occurrences of an arbitrary character. For example, the query below searches for pos (part-of-speech) annotations that begin with "VV", corresponding to all forms of lexical verbs (the auxiliaries "be" and "have" are tagged VB... and VH... respectively). The string "VV" means that the result must begin with "VV", the period stands for any character, and the asterisk means that 'any character' can be repeated zero or more time, as above.
This finds both finite verbs ("VVZ", "VVP", "VVD") and non-finite ones ("VV") or gerunds ("VVG"). It is also possible to search for explicit alternatives by either specifying characters in square brackets or longer strings in round brackets separated by pipe symbols. The first example below finds either "of" or "on" (i.e. "o" followed by either "f" or "n") while the second example finds lemma annotations that are either "be" or "have".
Finally, negative searches can be used as usual with the exclamation point, and regular expressions can generally be used also in edge annotations. For example, if we search for trees (see also Searching for Trees) where a lexical verb dominates another token with a dependency edge not containing 'obj', we can use a wildcard to rule out all edges labels containing those letters. This will give us all non-object dependants of lexical verbs:
pos=/VV.*/ & tok & #1 ->dep[func!=/.*obj.*/] #2
OR (using a shortcut):
pos=/VV.*/ ->dep[func!=/.*obj.*/] tok
While there is the POSIX-standard for regular expressions, different search engines might use slightly different syntax and support different types of search constraints, e.g. when searching for Unicode characters.
ANNIS used to rely on the PostgreSQL regular expression implementation but now uses the Rust library
regex. See https://docs.rs/regex#syntax for the currently supported regular expresssion syntax, as provided by this library.