Describes a hierarchical text database model and defines an algebra based on concordance lists. The algebra is presented as a theoretical model to define both a conceptual schema for the database and search protocols for database implementation. Several retrieval examples are included. (19 references) (MES)

Discusses the shift of information access from a data-centered to a user-centered model and describes the Daltext system, a prototype user-centered information system that allows the user to determine how the data will be viewed (i.e., within a datastream model, a set model, a relational model, and/or a hierarchical model). (Contains 30…

Proposes a new learning algorithm to improve the retrieval effectiveness of the search system used in the hypertext environment using an extended Boolean model with links to improve the ranking of retrieved items. Highlights include the basic retrieval scheme, the learning scheme, and a review of basic probabilistic retrieval models. (Contains 32…