4.2 Dominance Constraints
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:
