Message Simplification

1. Message Simplification Making Version 3 as easy to implement as Version 2 – but with sound semantics rpworden@me.com

2. Leaf Node Counts • One measure of the cost and complexity of reading and writing a message • The number of distinct node (types) which can each carry a distinct piece of variable data • Nodes you might need to map to a field in an application database – or write a piece of application logic to handle

3. Node Counts - Version 2 • OBX segment – 225 • ADT^A03 – 1885 • ORU^R01 – 4412 • OMP^009 – 5225

4. Node Counts - Version 3 • To keep the numbers down: • No recursive nesting • No nesting of data types • Ignore data type ANY • XML Attributes only • Lab Result Event (POLB_RM004000UV01): 101,792 nodes • Medication Order (PORX_RM010120UV): 38,882 nodes • CCD: 10,284,480 nodes

5. Is This Message Size Useful? • No application database has 50,000 columns • No system has data to populate 50,000 nodes • If it did, the costs of mapping the data to 50,000 nodes would be prohibitive • The cost of writing business logic to handle the data would be prohibitive • Most example instances have at most a few hundred node types populated

6. Why HL7 V3 is Difficult • 50,000 node types is too many • Finding the right nodes to read or write is not easy • To get to those nodes, you need to pass through a large superstructure of semi-fixed stuff • V3 is technically intricate; knowledge about it is still scarce and debated • The defining material is spread across many places

7. All V3 Implementations are Partial V3: 50,000 + nodes Implementations V2: 3,000 nodes Interoperability happens in the overlaps between implementations

8. The Simpler Way to Implement V3 • Interoperability depends on a group of suppliers and purchasers agreeing which subset of a V3 message they need. • The subset probably has no more than 1000 leaf nodes • Once this subset is agreed, it can be packaged into a much simpler message • The semantics of the simple message are fully defined, by reference to V3 semantics • Simple messages can be reliably converted to full V3 Messages, and vice versa, by XSLT

9. Message Simplification – The Process V3 RMIM (MIF) Templated RMIM (ECore) Select Annotated RMIM (Ecore) Rename Press the Button Simple Message Schema Skeleton Simple Message Simple-Full Transforms (XSLT) Simple-Full Mappings Simple Class Model (Ecore)

10. Uses of Simplification Products

11. Message Simplification Is Easy to Do • Select the nodes you want to retain in the simple message • Rename attributes and elements • Override automatic flattening rules (if you want) • Do these either with a special editor, or by annotating a message example • The tools do the rest automatically • The round-trip V3=>Simple=>V3 is easily tested

12. Using Simplified Messages Simple XML Simple XML V3 Application A Simple-to-Full Transform Full-to-Simple Transform Application B V3 Application C

13. Testing By Round Trips Full-to-Simple Transform V3 message Simple message Simple-to-Full Transform Should recover all you need of the V3 message, unchanged.

14. Potential • This approach can greatly reduce the costs of implementing Version 3 and CDA • It can make V3 as easy to implement as V2 – but with sound V3 semantics • It can greatly increase the takeup of V3 and CDA • This benefits everybody • Suppliers and purchasers can collaborate to define message simplifications, under the auspices of HL7 • HL7 can make transforms and other deliverables available to members