The generality and expressive power of the topic map model bring with it other advantages that go far beyond those traditionally associated with indexes. The close similarity to semantic nets gives an idea of how topic maps, even without any occurrences connecting them to an information pool, can become valuable resources in their own right. This in turn opens up new business opportunities for creating and selling “portable topic maps” that can be overlaid on multiple information pools. For traditional commercial publishers, producing well-crafted topic maps could be a new way of leveraging their existing knowledge and experience and combating the threat to their existence posed by the vast amounts of information now available for free.