Writing an replacement execution context

This document is intended to be read by people who are capable of Java programming.

Replacing the execution context of Arden2ByteCode means providing a class that serves as information gateway to the "outer world" of a Medical Logic Module. Thus, via an execution context, you can integrate Arden2ByteCode into your data infrastructure.

Any execution context should be a subclass of the abstract class arden.runtime.ExecutionContext. Also a class arden.runtime.BaseExecutionContext exists, providing a simple implementation of the call statement.

The following methods of arden.runtime.ExecutionContext may be overridden:

• public DatabaseQuery createQuery(String mapping)
  This method is called when a read statement like read last 3 from {select * from person} in a MLM (Medical Logic Module) is executed.
  The string mapping contains whatever the braces of the read statement contain (select * from person as of the example). These strings are specific to the environment the MLM is attached to. In the above example, I used SQL syntax, because Arden2ByteCode provides an execution context where the mapping is passed to a JDBC SQL driver specified by the user.
  You may use the mapping string for whatever information you need to pass from the MLM to the execution context.
• public ArdenValue getMessage(String mapping)
  This method is called when a message is assigned using the MESSAGE statement.
  An example would be:
  msg := MESSAGE {pneumonia};
  In this example pneumonia would be the mapping string.
• public void write(ArdenValue message, String destination)
  This method is called when a write statement is executed.
  Example: WRITE "hello" at dest;
  Here, message would be "hello" and destination would be the destination mapping previously created with a line like dest := destination{mapping};.
• public ArdenRunnable findModule(String name, String institution)
  This method is run, when another MLM is referenced in a data assign phrase.
  Example: find_allergies := MLM {find_allergies from my_institution};
  In the above example, find_allergies is the module name string and my_institution is the institution string.
• public ArdenRunnable findInterface(String mapping)
  This method is called, when an interface statement with the specified mapping is executed.
• public void callWithDelay(ArdenRunnable mlm, ArdenValue[] arguments, ArdenValue delay)
  This method is executed, when a call statement with a delay is executed.
  Example: mlmx := MLM 'my_mlm' CALL mlmx DELAY 3 days;
• public ArdenTime getEventTime()
  This method is called, whenever EVENTTIME is called in a MLM.
• public ArdenTime getTriggerTime()
  This method is called, whenever TRIGGERTIME is called in a MLM.
• public ArdenTime getCurrentTime()
  This method is called, whenever NOW is stated in a MLM.

You may implement these methods as of your needs.
The classes arden.runtime.BaseExecutionContext and arden.runtime.StdIOExecutionContext provide examples of how to implement these methods.

If you e.g. try to attach a MLM to a certain database or any other datasource, you can for example override the createQuery() method and pass the parameters to your database query parser.

The write() and getMessage() methods are intended to inform the user of MLM messages. They could be implemented as to display information on a GUI or web interface.

findModule() and callWithDelay() are intended to load other MLMs but they can also serve as interface to your IT infrastructure meaning you can load programs written in other languages than Arden Syntax as well if you want that.