We use rooted, labeled trees as our model for structured data. These
are trees in which each node n has a label l(n) that is chosen
from an arbitrary domain 
. The problem of snapshot change
detection in structured data is thus the problem of finding a way to
edit the tree representation of one snapshot to that of the other. We
denote a tree T by its nodes N, the parent function p, and the
labeling function l, and write T = (N,p,l). The children of a
node 
are denoted by C(n).
We begin by defining the tree edit operations that we consider. Since there are many ways to transform one tree to another using these edit operations, we define a cost model for these edit operations, and then define the problem of finding a minimum-cost edit script that transforms one tree to another.