Systems and methods for data storage, retrieval, manipulation and display provide search engines and computer-based research tools for enabling multiple hierarchical points of view. Category definitions in the hierarchical data structures can include lists of set members, like word arrays of set members, generative descriptions for determining set members, and fitness functions for determining fitness of a presented item for being a member of a set. Significance and interest values can be assigned to search categories to set threshold confidence levels for returning search results and for weighting the results, respectively. A user interface can present results in the form of browsing multiple hierarchical representations, wherein matching categories are differentiated from non-matching categories. Peer ratings can represent the ranking of search term results with relation to results using other search terms, providing an indication of the fitness of the search terms for returning satisfactory results.