distributed DBMSs. When a relation needs a lot of processing power and a higher disk access bandwidth , the relation can be declustered as a hor- izontally partitioned relation and located in element DBMSs. When a relation is frequently accessed, some replicas of the relation can be made and located in element DBMSs. However, in the current implementation, the replicated relation can be used only for the global map, that is, for server DBMSs. Relations can be located in main memory and/or secondary memory in an element DBMS. Relations which are located only in main memory are temporary relations. Quasi main memory relations both in secondary memory and in main memory provide guarantees that the modifications are reflected in the secondary memory. Query Processing There are two types of command for query processing: primitive com- mands and KQL, a query language based on extended relational algebra. Primitive commands are the lowest operations for relations, and can treat relations efficiently. KQL is syntactically like KL1. New operations can be defined temporarily in a query. A query in KQL is translated into sub-queries in intermediate operations for extended relational algebra, and is submitted to the relevant element DBMSs. A query in primitive commands is submitted to the relevant element DBMSs. The query is processed as a distributed transaction among the relevant element DBMSs, and is finished under the control of a two-phase commitment protocol. Parallel Processing Kappa-P parallel processing takes the form of inter-cluster parallelism among element DBMSs and intra-cluster parallelism in an element DBMS. Inter-cluster parallelism provides more processing power, but also in- creases communication overhead. The trade-off is between processing power and communication overhead. Intra-cluster parallelism is suitable for a DBMS manipulating large amounts of data. Kappa-P uses the parallelism for internal processing of an ele- ment DBMS, for instance parallel processing by tuple stream, operations for set, and index operations of temporary relations. - 77 -