To answer the original question.  InterSystems provides detailed class documentation.  For SQL tables, columns in general will map to class properties.  See if this link provides what you are looking for.

https://docs.intersystems.com/latest/csp/documatic/%25CSP.Documatic.cls?APP=1&LIBRARY=ENSLIB&CLASSNAME=EnsLib.HL7.Message

Chris, 

Great tutorial.  Was able to get this all working fairly easy against an InterSystems IRIS for Health environment.  Looking forward to the next section.

Ken

Okay, looked at the docs more and my eyes were playing tricks on me.

Looks like you cant call a routine at a tag in another namespace, but can call a routine at the top in another namespace.

The syntax is:

do ^|"namespace"|routine

so:

do ^|"SAMPLES"|YJM