The extended relational model, RM/T, based on ER model has been proposed as a semantic data model. This thesis presents a model of query processing in RM/T. In order to handle the join operations effectively, we group the query steps related to the same entity type so that the search space in optimization phase is considerably reduced.
Conventional method is used for inter group joins. And to optimize intra group joins, four methods performing all the join operations in a group are described and evaluated. As the result, joining the relation with minimum cardinality first by sort-merge shows the best performance.