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We now present a formal language with which we can write tree descriptions. This is the language of Dominance Constraints with Set Operators as described in [DN00]. It has the following abstract syntax:
where variables denote nodes and
.
represents proper dominance and
disjointness. The constraint
is satisfied when the relationship that holds between
and
is one in
. Thus
is satisfied either when
and
are equal, or when they denote nodes in disjoint subtrees. We write
instead of
and generally omit braces when we can write a single symbol.
Consider again the scope ambiguity example:
It can be expressed as the following dominance constraint:
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