10. The machine-readable memory device of claim 9 , wherein determining the target object comprises selecting an object from the plurality of objects with a highest score.
9. The machine-readable memory device of claim 8 , wherein assigning weight values to nodes other than the set of leaf nodes further comprises: determining whether an expression represented by the node evaluates as false; and in response to determining the expression represented by the node evaluates as false, scoring each child node of the node as zero.