Performance of using Oracle XMLDB in the evaluation of CDISC ODM for a clinical study informatics system

This paper describes potential strategies for data modeling and implementation as part of the general architecture of CSIS, a clinical study and informatics system that has been developed for the National Institute of Neuroscience and Stroke (NINDS). We discuss the NINDS requirements and how they influenced the system design, with an emphasis on dynamic form creation. We also evaluate open standards such as "CDISC ODM" and several database technology choices, namely conventional relational "EAV" tables and the new "XMLDB" from Oracle. We describe performance test results, which show that it is feasible to implement CDISC ODM in Oracle XMLDB and the schema-based storage option for storing XML content is better than "CLOB"-based for applications that require high numbers of queries for XML fragments. For storage and retrieval of whole XML documents, CLOB storage is optimal. CSIS implements a hybrid approach of combining CLOB storage for storing XML documents with relational tables for storing metadata. Due to the complexity of the CDISC schema and related performance and implementation concerns, we have decided not to implement CDISC internal storage in our system.