Adding HL7 version 3 data types to PostgreSQL

TL;DR

This paper analyzes HL7 v3 data types for database implementation, proposes improvements, and demonstrates an effective PostgreSQL extension that supports complex medical data types and operations with better performance.

Contribution

It provides a detailed analysis of HL7 v3 data types, suggests specification improvements, and implements a PostgreSQL extension for efficient handling of complex medical data types.

Findings

PostgreSQL can effectively execute calculations with HL7 data types.

User-defined types outperform standard database types in synthetic tests.

The implementation supports operations similar to medical terminology servers.

Abstract

The HL7 standard is widely used to exchange medical information electronically. As a part of the standard, HL7 defines scalar communication data types like physical quantity, point in time and concept descriptor but also complex types such as interval types, collection types and probabilistic types. Typical HL7 applications will store their communications in a database, resulting in a translation from HL7 concepts and types into database types. Since the data types were not designed to be implemented in a relational database server, this transition is cumbersome and fraught with programmer error. The purpose of this paper is two fold. First we analyze the HL7 version 3 data type definitions and define a number of conditions that must be met, for the data type to be suitable for implementation in a relational database. As a result of this analysis we describe a number of possible improvements in the HL7 specification. Second we describe an implementation in the PostgreSQL database server and show that the database server can effectively execute scientific calculations with units of measure, supports a large number of operations on time points and intervals, and can perform operations that are akin to a medical terminology server. Experiments on synthetic data show that the user defined types perform better than an implementation that uses only standard data types from the database server.