Query decomposition in an object-oriented database system distributed on a local area network

Several issues are discussed concerning query processing in the framework of COMANDOS. COMANDOS is an object-oriented system supporting the development of distributed advanced applications. We first summarize the data model and the query language. Then we present the architectural aspects that are relevant for query processing. Finally we describe query decomposition and optimization. Two different strategies for join execution are discussed. The first is based on a distributed execution using semi-join operations. The second is based on first centralizing all relevant data on a server machine, and then executing all join operations locally at the server. The second strategy may be useful when the data are distributed on a large number of nodes which have limited processing power. In this case, it may be more efficient to use a dedicated server machine for query executions