A straightforward NF2 relational interface with applications in information retrieval

摘要

In information retrieval (IR) there is a need for greater structural expressiveness than that provided by ordinary retrieval systems or the ordinary relational model. Especially hierarchical structures are usual in IR applications. Therefore the non-first-normal-form (NF2) relational model often is a more natural and intuitive way to model data of IR applications than the pure relational model. Because many-to-many relationships often exist among real world entities of IR applications, it is impossible to find a stable hierarchical structure suitable to all needs of users. This means that a tool is needed that has a powerful restructuring capability. In other words, it has to be able to produce for the user result NF2 relations in which hierarchical relationships among data have been organized in a way that is drastically different from that in the source NF2 relations. In this paper we classify typical data restructuring tasks in an IR environment, and give several examples on their specifications. It has been widely recognized that NF2 relational query formulation with conventional query languages is too cumbersome for ordinary end users. In order to simplify NF2 relational query formulation, we have developed and implemented a novel user interface. We show that query specification in this interface remains compact and truly declarative—also in the context of complex NF2 relational queries.