There are fixed selection fields and free selection fields.
In the fixed selection fields (like Type and Status) there is a list of pre-defined values to choose from.
In the free selection fields, the user can supply a regular expression.
Only entries for which all fields are matched by the corresponding regular
expression are selected (an empty field does not impose any restriction).
Matching is case insensitive.
A regular expression is zero or more branches, separated by ``|''. It matches anything that matches one of the branches.
A branch is zero or more pieces, concatenated. It matches a match for the first, followed by a match for the second, etc.
A piece is an atom possibly followed by ``*'', ``+'', or ``?''. An atom followed by ``*'' matches a sequence of 0 or more matches of the atom. An atom followed by ``+'' matches a sequence of 1 or more matches of the atom. An atom followed by ``?'' matches a match of the atom, or the null string.
An atom is a regular expression in parentheses (matching a match for the regular expression), a range (see below), ``.'' (matching any single character), ``^'' (matching the null string at the beginning of the input string), ``$'' (matching the null string at the end of the input string), a ``\'' followed by a single character (matching that character), or a single character with no other significance (matching that character).
A range is a sequence of characters enclosed in ``[]''. It normally
matches any single character from the sequence. If the sequence begins
with ``^'', it matches any single character not from the rest of the sequence.
If two characters in the sequence are separated by ``-'', this is shorthand
for the full list of ASCII characters between them (e.g. ``[0-9]'' matches
any decimal digit). To include a literal ``]'' in the sequence, make it
the first character (following a possible ``^''). To include a literal
``-'', make it the first or last character.
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| whose title contains "logic" | enter logic in the Title field |
| whose title contains "logic" or "specification" | enter logic|specification in the Title Field |
| whose title begins by "non" | enter ^non in the Title field |
| from the years 1995 to 1998 | enter 199[5-8] in the Year field |
| whose title contains "specification" before "logic" | enter specification.*logic in the Title field |
| that appear in serials | enter .* in the Serial field (this requires the field to be not empty, and is differente from leaving the field empty) |