Using relational algebra on the specification of Slowly Changing Dimensions - a first step

Data Warehouses are refreshed periodically with data from source systems. Nevertheless this data is not only related to new facts, but also to dimension data. Some dimensions have the particularity of evolving through time, either by having new data or by changes that occur in source systems and must be reflected in the data warehouses. Dealing with these, so called, Slowly Changing Dimensions is a complex task that the Extract, Transform and Load process is responsible. Common approaches are based on typing these dimensions and act accordingly, which adds to the already complex nature of the process. In this paper we analyze these different types of slowly changing dimensions, proposing a relational algebra specification to deal with them.