Descriptions of feature values may be complex in the sense that type symbols and strings can be combined as Boolean expressions. The operators are ! (negation), & (conjunction), and | (disjunction). Here are uses of a Boolean expressions as a feature value descriptions:
[pos = ("NN" | "NE")]
[pos = ! ("NN" | "NE") ]
By the way, the query above can be written as:
[pos != ("NN" | "NE") ]
Please note: Boolean expressions for feature values which involve binary
operators (conjunction and disjunction) must always be put into
parentheses. See the example above where the outer parentheses
cannot be omitted!
The operator precedence is defined as follows: !, &, |. This definition is illustrated by the following examples:
Example | Interpretation |
! "NN" & "NE" | (!"NN") & ("NE") |
"NN" & "NE" | "PREL" | (NN"&"NE") | ("PREL") |