mirth - HL7 Segment - Message type Vs segments

Question

Are there any restrictions on the Segments that should be used for a Specific message type? For Ex: If I have to create a sample HL7 ADT^A05 or REF message.. Can I include any segment that I like, or HL7 has some rules defined to choose the segments for specific message type?

Is the below Hl7 Message correct?

MSH|^~&|DASH|DASH-GCD|CentralLogic|COCXXX|20130730183557||REF^I12|20130730183339|P|2.3.1|||AL|AL
PID|0||26||Test^Patient^^^||19950115|M|||||Phone#^Email||||||SSN#|PD1|||||PCP FName^LName|RF1|Pending|Patient ETA|Direct Admit|Doc-to-Doc|Critical|Admission#||||Note Info|PRD|RP|Smith^Ken^|1600 Medical Center Way^^Eureka^CA^95521||(707)555-5555||NPI#PRD|RT|Pacific Heart Group^Physician Name|Admitting Facility Name||(707)444-8300
NUP|Bed Location|Bed StatusIN1|1|||Insurance Company Name|Patient Gr ID|Patient Member ID||||||||IN2|Insured’s Employee ID|Insured’s Social Security Number|Insured’s Employer Name|OBX|1|CE|1010.1^BODY WEIGHT||154|LBOBX|2|CE|1010.1^HEIGHT||75|INDG1|1|I9|786.59|Chest pain||DG1|2|I9|794.31|Sun Burn||AL1|1|DRUG|Codeine|AL1|2|DRUG|PCN|RXO|CE|Albuterol 2.5 mg via Ben q6h prn sob||||||ODT|CE||Test Instruction

Answer 1

1. HL7 defines sets of messages and recommended segments. Exact valid form depends on the HL7 conformance profile that your and the-other system support.

For an example of conformance profiles and some tool to use it see e.g. http://hl7api.sourceforge.net/conformance.html

2. For list of conceptually valid segments in particular messages check appropriate version of the HL7 specification at http://www.hl7.org/implement/standards/product_brief.cfm?product_id=185.

In case of your message take a look at "HL7 Messaging Standard Version 2.3.1". For more up-to-date specification with better description look at "HL7 Messaging Standard Version 2.5" as this version is said to be (no proof available) most elaborate out of the HL7 2.x range.

3. For conceptual overview of messages and their meaning and system-wide IHE integration profiles refer to recommendations provided by http://www.ihe.net/Technical_Frameworks/

4. Useful piece of software that can help you diagnose/validate basic HL7 structure is Inner Harbour Software's HL7Spy

I'm not an expert just providing some links to get you started