Relational algebra for ranked tables with similarities: Properties and implementation

The paper presents new developments in an extension of Codd's relational model of data. The extension consists in equipping domains of attribute values with a similarity relation and adding ranks to rows of a database table. This way, the concept of a table over domains (i.e., relation over a relation scheme) of the classical Codd's model extends to the concept of a ranked table over domains with similarities. When all similarities are ordinary identity relations and all ranks are set to 1, our extension becomes the ordinary Codd's model. The main contribution of our paper is twofold. First, we present an outline of a relational algebra for our extension. Second, we deal with implementation issues of our extension. In addition to that, we also comment on related approaches presented in the literature.