An Examination of Multi-Tier Designs for Legacy Data Access

This work examines the application of Java and the Common Object Request Broker Architecture (CORBA) to support access to remote databases via the Internet. The research applies these software technologies to assist an Air Force distance learning provider in improving the capabilities of its World Wide Web-based correspondence system. An analysis of the distance learning provider's operation revealed a strong dependency on a non-collocated legacy relational database. This dependency limits the distance learning provider's future web-based capabilities. A recommendation to improve operation by data replication is proposed, and the implementation details are provided for two alternative test systems that support data replication between heterogeneous relational database management systems. The first test system incorporates a two-tier architecture design using Java, and the second system employs a three-tier architecture design using Java and CORBA. Data on replication times for the two-tier and three-tier designs are presented, revealing a greater performance consistency from the three-tier design over the two-tier design for varying client platforms and communications channels. Discussion of a small-scale proof-of-concept system based on the three-tier design is provided, along with a presentation of the potential for the technologies applied in this system to benefit Air Force web-based distance learning.