Hans JonkersPhilips ResearchOctober 27, 2009

The ABCD HL7v3 Generator

Philips Research, October 27, 2009 2

The ABCD HL7v3 Generator

Maps the MIF and XSD sources of the HL7v3 standard to C# code that• supports the creation, access, modification, storage and retrieval of

HL7v3 objects • is strongly-typed: each (data, vocabulary, RIM, etc.) class/type is

mapped one-to-one to a type defined in C#• is independent of the way the objects are stored (in-memory, in XML or

in a database)

ABCD HL7v3Generator

C#

C# API

MIF

XSD

HL7v3 Standard

Restrictions:• No support for the HL7v3

methodology• No support for the

messaging part of HL7v3

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Example

Creating an encounter:

var patient = Patient.LoadInstanceFromXml( ... );var practitioner = Practitioner.LoadInstanceFromXml( ... );var encounter = new Encounter();var subject = new Subject( patient, encounter );var performer = new Performer( practitioner, encounter );encounter.moodCode = ... // Fill in the encounter details...encounter.SaveInstanceToXml( ... );

PersonA

PersonB

Patient

Practitioner

Subject

Performer

Encounter

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Example (Visual Studio)

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Development Process In A Nutshell

1. Use model-driven development– Technology used: MOM (Meta Object Model) + Vampire toolset

2. Generate a MOM object model + XML reader from the XML schema definition of MIF.

3. Use model-to-model transformations to map the MOM representations of the MIF artifacts to MOM object models.

4. Generate C# code from the MOM object models:

object modelgenerator object model

C#generator

C#

C# API

MIF

XSD

HL7v3 Standard ABCD HL7v3 Generator

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Generator Network

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VIDE Snapshot of MifModel.mom

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VIDE Snapshot of RIM

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VIDE Snapshot of Clinical Statement

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Current Application of the Generator

• Small XML repository of patient data (to be extended)• Object model hierarchy:

Datatypes(R1)

Vocabulary

RIM(2.26)

R_PatientUniversal

ClinicalStatement

R_AssignedEntity

Universal

R_AssignedPerson

Identified

R_MedicationUniversal

R_SpecimenUniversal

CMETs …..

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Visual Studio Screenshot

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Some Problems Encountered

• Understanding the constructs of the MIF language was often a matter of experimental informatics (due to a lack of documentation)

• Not succeeded in generating a complete set of consistent MIF files (using the official HL7 V3 Generator) from the set of tool input files

• MIF R1 datatype specification too abstract to generate code from → XML schema file of data types was used to generate code from

• Vocabulary contains duplicate codes (within same coding system) and uses multiple concept inheritance at a few places

• Stacking of static models pushes Visual Studio to its limits; need some way of flattening the models

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Some Useful Techniques

• Model-to-model transformations make life a lot easier than transformations at the XML level (using XSLT)

• The ability to define metametamodels (MetaRim, MetaVoc) allows RIM-flavor to be added to object models

• Union types are a very natural way to deal with HL7v3 choice boxes• Partial class mechanism of C# is very useful to keep different aspects

of code generation separated

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Conclusion

• MIF + (light-weight) Model-Driven Development is a good marriage• XML can be kept under the hood• Current generator is still a prototype, but sufficient to build basic RIMBAA

apps based on MIF-definitions of HL7v3 static models

Possible improvements/extensions:• Generation of more ‘convenience functions’• Moving structural attributes to the metatypes• Support for extension/restriction at the modeling level• Support for MIF constructs that are not currently used• Generation of validation code• Support for message handling• Turn MOM into a light-weight HL7v3 MDD formalism (as opposed to

UML) ???