1. An information source alignment system comprising: a processor coupled to a memory; a tree generation module to generate a source category hierarchy tree for a source class in a first information source and a target category hierarchy tree for a target class in a second information source, wherein the source and target category hierarchy trees are constructed from a class hierarchy of a knowledge source; a class-similarity determination module comparing the source and target category hierarchy trees; a contextual-similarity determination module determining a similarity between superclasses of the source and target classes, the superclasses being ascertained from the respective first and second information sources; and an alignment module determining whether the source and target classes are aligned based on the comparison of the source and target category hierarchy trees, and based on the determined similarity, wherein the contextual-similarity determination module determines a number of superclasses of the source and target classes that are supported by the source and target category hierarchy trees, and wherein the class-similarity determination module identifies common nodes between the source and target category hierarchy trees for calculating a class-similarity value based on the category hierarchy tree comparison.