The layout algorithm used in the current implementation of WebMap
to calculate the node positions for a spanning tree is based on
the following principles:
Assume a new node is to be inserted into an existing tree as child
After determining the position of the new node 
.
The precondition is characterized by:
The y-coordinate of incremented by one.
If
the x-coordinate will be the same
as
.
's rightmost descendant
incremented by 2.
all nodes
of the tree ``above'' and ``to the right'' of
are moved to
a new position using a simple recursion:
This is illustrated in Fig. 5. The nodes which moved to the
right after the insertion of a new node with the x-coordinate 8 are
surrounded by a dotted line.
and the nodes
of their subtrees are incremented by two.
is incremented by one.
to
its parent node and repeat this procedure.
The algorithm causes each node to be located one level above its children
and in the middle between its leftmost and its rightmost descendant,
which means that its x-coordinate
always satisfies the following
equation:
Here
's leftmost descendant and
's subtree.
Note, that all node's coordinates are represented by integer values.