Superimposing codes representing hierarchical information in web directories

In this article we describe how superimposed coding can be used to represent hierarchical information, which is especially useful in categorized information retrieval systems (for example, Web directories). Superimposed coding have been widely used in signature files in a rigid manner, but our approach is more flexible and powerful. The categorization is based on a directed acyclic graph and each document is assigned to one or more nodes, using superimposed coding we represent the categorization information of each document in a signature. In this paper we explain the superimposed coding theory and how this coding technique can be applied to more flexible environments. Furthermore, we realize an exhaustive analysis of the important factors that have repercussions on the performance of the system. Finally we expose the conclusions obtained from this article.