Getting to know HL7v2 and HL7v3

How to quickly learn HL7v2

1. Download HL7v2 specification, e.g you can get a copy from HL7 v2.3.1 specification from HL7 web site, or other HL7v2.x specification from HL7 web site
2. Read CH2fin.doc to understand the conceptual approach, HL7 message/segment/field, encoding rules, data type, acknowledgement.
3. Pick a domain you are going to work on, such as "Ch3fin.doc" for patient administration, "ch7fin.doc" for observation report.

How to quickly learn HL7v3

1. Prerequisite - have basic understanding of UML modeling concepts such as inheritance, association, etc

2. (Optional) You can read Modeling in Color to understand why the class model in HL7v3 is color coded. You can go to this page to see HL7v3 color representation for the various types of classes.

3. (Optional) Read this wonderful article Data Model Quality: Where Good Data Begins, and also please scroll down to the bottom to read the reference #3 by Matthew West "Developing High Quality Data Models, Volume 1, Principles and Techniques" back in 1994

4. Read HL7v3 RIM at Latest HL7v3 Reference Information Model, focus on the following back bone classes, dont be so eager to know everything
   a) Act
   b) ActRelationship 
   c) Entity
   d) Role
   e) Participation
When you browse through these classes, you can directly jump to the corresponding data type specification or vocabulary as listed below

5. Refer the corresponding HL7 v3 data type at HL7 v3 Data Type R2

6. Understand HL7 vocabulary at HL7v3 Vocabulary  to have understanding on the meaning of the categories of code. In laymen's term, this defines a set of code with corresponding description such as the list of code for purchase order status. Of course focus on the following code
     a) ActClass
     b) EntityClass
     c) RoleClass
     d) ParticipationType
     e) ActRelationshipType