Basics

Several features of Arden Syntax interaction are summarized below. For a more detailed description of the Arden Syntax, see HL7's Arden Syntax definition.

Medical Logic Modules (MLMs)

In an Arden Syntax knowledge base, medical knowledge is divided into medical logic modules (MLMs). Each MLM contains instructions and logic to support at least a single medical decision, and has the file extension .mlm.

Calling MLMs

MLMs are managed by a runtime environment called the ArdenSuite engine. The ArdenSuite engine manages a collection of compiled MLMs and handles communication with requesting entities. With the ArdenSuite engine assuming these tasks, the host system no longer needs to concern itself with MLM implementation or location specifics; when the host system calls an MLM, the ArdenSuite engine reacts by executing the respective MLM and returning the result (= output) to the host system:

There are three ways to call an MLM:

• Direct invocation: An MLM is executed by a direct call specifying its name and institution.
• Event call: All MLMs that are registered to and listening for a certain event are executed upon the occurrence of that event.
• Delayed call: An MLM is executed upon a specified point of time, or a specified period after the occurrence of an event it is registered for.

Data In- and Output

MLMs implement medical knowledge and apply this knowledge to input data, after which results are sent back to the requesting entity. The interaction between an MLM and the requesting entity (i.e., the host system) is illustrated below:

There are several ways a host system and an MLM can interact with each other:

• Input parameters: Data is sent to the MLM during an MLM call or event call.
• Curly brace expressions: These expressions are a provision within the Arden Syntax for dynamic interaction between an MLM and an external (host) system. Examples of such interaction include querying a database or calling external functions.
• Write statements: Data can be written to predefined destinations. These definitions are implemented through connectors in the ArdenSuite Server.
• Result output: After the successful execution of a MLM, results can be sent back to the calling host system.