Working Together in Harmony — An Implementation of the CORBA Object Query Service and its Evaluation

The CORBA standard, together with its service specifi-cations, has gained considerable attention in recent years. The CORBA Object Query Service allows for declarative access to heterogeneous storage systems. We have come up with an implementation of this service called Harmony. The objective of this article is to provide a detailed description and quantitative assessment of Harmony. Its main techni-cal characteristics are data-flow evaluation, bulk transfer, and intra-query parallelism. To carry out the evaluation, we have classified data exchange between components of appli-cations in several dimensions: one is to distinguish between point-, context- and bulk data access. We have compared Harmony with (1) data access through application-specific CORBA objects, and (2) conventional client/server commu-nication, i.e., Embedded SQL. Our results show that Har-mony performs much better than Alternative 1 for bulk data access. Besides that, due to the features mentioned above, Harmony performs approximately as well as conventional client/server communication mechanisms. 1