Embodiments of articles, apparatuses, devices and/or systems for manipulating hierarchical sets of data are disclosed. For example, in one embodiment, a method of transforming one or more trees to one or more corresponding symbol strings according to an association of trees and symbol strings is disclosed. In another embodiment, as another example, a method of transforming between at least a first and at least a second expression is disclosed in which the expressions have a common view that is other than one. Additional embodiments are also described.