15
Ranked Trees as Structures
Lets restrict to Rank(
S
) = 2
easy to generalize
Let
s
= {<, (P
a
)
a
2
S
, succ
1
, succ
2
}
Consider only structures in STRUCT[
s
]
that are trees, where < is the ancestor-
descendant relation, and succ
1
, succ
2
are the
left and right child respectively