Executing medical logic modules expressed in ArdenML using Drools

Abstract

The Arden Syntax is an HL7 standard language for representing medical knowledge as logic statements. Despite nearly 2 decades of availability, Arden Syntax has not been widely used. This has been attributed to the lack of a generally available compiler to implement the logic, to Arden's complex syntax, to the challenges of mapping local data to data references in the Medical Logic Modules (MLMs), or, more globally, to the general absence of decision support in healthcare computing. An XML representation (ArdenML) may partially address the technical challenges. MLMs created in ArdenML can be converted into executable files using standard transforms written in the Extensible Stylesheet Language Transformation (XSLT) language. As an example, we have demonstrated an approach to executing MLMs written in ArdenML using the Drools business rule management system. Extensions to ArdenML make it possible to generate a user interface through which an MLM developer can test for logical errors.

Figure 1

An approach to implementing Arden Syntax Medical Logic Modules (MLMs) in the Drools run-time environment. Arden expressed as ArdenML is converted to executable code using Extensible Stylesheet Language Transformations (XSLTs). The files produced include Drools rules and a mechanism for invoking them. An additional file provides a user interface allowing testing of the rules.

Figure 2

A user interface for testing a Medical Logic Module (MLM). Display and data entry components are defined in the curly braces part of Arden data definition statements. An Extensible Stylesheet Language Transformation (XSLT) converts this syntax into JSP code defining relevant fields on a web-based data entry form.

Figure 3

(A) A simple rule in Arden Syntax. Only the knowledge category is shown in full. This Medical Logic Module (MLM) reminds the clinician of the need for routine monitoring of HgA1C in patients with diabetes. (B). The same MLM expressed in ArdenML. The XML-based format for MLM expression provides an opportunity to manipulate the logic and to convert it into other forms.