FHIR for Architects and Developers

Acknowledgements• Lloyd McKenzie• Ewout Kramer• Grahame Grieve

Agenda

• Architectures• Paradigms• Resources• Bundles• Profiles & Extensions• Server Notes• Workflow• Security• Tools and Help• Next steps in New Zealand

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The Spec: Hl7.org/fhir

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Architectures

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Architectures

• FHIR makes no assumptions about the architectural design of systems

• You can use it for– Light or heavy clients– Central server or peer-to-peer sharing– Push or pull– Query or publish/subscribe– Loosely coupled or tightly coupled environments With history tracking (versions) or without

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Some possibilities

FHIR

Broker

v3

v2

PHR

FHIR

App

Comm.Interface

DB

FHIR

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Repository model

Vendor Neutral Repository

FHIR

HIS GP PACS SystemX Gateway

FHIR FHIRFHIRFHIR

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Beyond exchange

v3

v2

Other

X12

Broker

v3

v2

FHIR

Repository

Decision Support

FHIR

FHIR

Other

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Bottom Line

• FHIR is a set of tools– Defined resources– Extensibility mechanism– Versioning– Multi-paradigm– Set of standard interfaces– Support for complex services

• Primary purpose is interoperable data exchange• However, it can be leveraged in many ways

– Many we haven’t even thought of yet . . .

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Paradigms revisited

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Paradigms

• FHIR supports 4 interoperability paradigms

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REST Documents

Messages Services

What should you use when?

Paradigms: REST

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REST

• Simple, out-of-the-box interoperability• Leverage HTTP: GET, POST, etc.• Pre-defined operations

– Create, Read, Update, Delete– Also: History, Read Version, Search, Updates, Validate, Conformance &

Batch (Transaction)

• HTTP Headers for various options– Like resource format or location

• Response codes to indicate outcome– OperationOutcome Resource

• Works best in environments where control resides on client side and trust relationship exists

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Rest

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Creating & Updating

• POST vs PUT• Headers

– Request• Content-type• Location (for version aware)

– Response• Content-type• Others...

• Status messages– Standard HTTP

• OperationOutcome• Version aware updates

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Querying by REST

• Base queries– Simple GET against a resource type– GET [base]/Patient?name=eve

• Defined rules for query parameters

• More complex– _include– Tags

• Queries across reference– Eg conditions for a patient– GET [base]/Condition?subject=84238862– Chained queries

• Compartments– Syntactic sugar– GET [base]/Patient/84238862/Condition

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Synchronizing

• History of all resources on server– GET [base]/fhir/_history

• History of all patient resources on server– GET [base]/Patient/_history

• History of specific patient on server– GET [base]/Patient/1/_history

• A history of all changes: inserts, updates and deletions, ordered by newest first

• Limit with _since and _count

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What’s a ‘deleted’ Resource?

• Delete using DELETE verb• Trying read operations will return in a 410 (Gone) result in

stead of 404 (Not Found)• The resource will not be returned by the search operation.• You can “undelete” by doing an update (PUT) with fresh

content• Just a “marker” in a resource’s history

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Version history - deletions

33, v12 – 2012-12-04

33, v13 – 2012-12-05

33, v14 – 2012-12-08

/server.org/fhir/Patient/33/_history/12

/server.org/fhir/Patient/33/_history/14

/server.org/fhir/Patient/33/_history/13

/server.org/fhir/Patient/33/_history/15

/server.org/fhir/Patient/33

33, v15 – 2012-12-09

33, v16 – 2012-12-10

DELETION

/server.org/fhir/Patient/33/_history/16

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Version history - revival

33, v13 – 2012-12-05

33, v14 – 2012-12-08

/server.org/fhir/Patient/33/_history/14

/server.org/fhir/Patient/33/_history/13

/server.org/fhir/Patient/33/_history/15

/server.org/fhir/Patient/33

33, v15 – 2012-12-09

33, v16 – 2012-12-10

/server.org/fhir/Patient/33/_history/16

33, v17 – 2012-12-11/server.org/fhir/Patient/33/_history/17

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Batch

• POST a bundle to server root• Processed as a transaction

– All succeed, or all fail

• All operations supported• Different to /message endpoint

– /message allows custom server processing– Batch is a sequence processed as a transaction

Playing with FHIR

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Test Servers

• Servers– At least 4 to choose from– http://spark.furore.com/fhir/Patient/nz100– http://fhir.healthintersections.com.au/open/Patient/100– fhir.orionhealth.com/blaze/fhir/Patient– https://his-medicomp-gateway.orionhealth.com/blaze/fhir/metadata

• Tools– XML Editor (Oxygen) – REST Client (POSTMan)

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Script• Search patient on name • GET single patient from list

• XML & JSON • Update and PUT back • repeat REST Search • Show error

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When to use REST?

• Want low coupling between systems– In theory, very little up-front negotiation required

• Small, light-weight exchanges• Focus is CRUD operations

– Also for publish/subscribe

• Client-driven client-server orchestration• Server endpoint has fixed location• Well-suited for Mobile, PHR, Registries

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Rest

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When to avoid REST?

• Complex or server-driven orchestration– Order of operations matters (e.g. complex decision support)

• Unit of work != resource– “Transaction” may be an option

• Lack of trust in the client for audit, etc.

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Rest

Paradigms: Documents

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Documents

• Similar to CDA• Collection of resources bound together

– Root is a “Composition” resource– Just like CDA header

• Sent as an ATOM feed– Usually stored as binary blob– Can be separate resource with Composition as ‘entry’ point

• One context– Not propagated

• Can be signed, authenticated, etc.• Working on conversion between FHIR Doc & CDA

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Documents

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Documents – are bundles

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Observation Resource

Composition Resource

SectionSection

Device Resource

Patient Resource

Prescription Resource

<feed> <entry> <Composition /> </entry> <entry> <Observation /> </entry> <entry> <Device /> </entry> <entry> <Prescription /> </entry> <entry> <Patient /> </entry></feed>

AttesterMetadata

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The Composition resource

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Document Management

• The DocumentReference resource– Enables ‘XDS-like’ services

• The ‘registry’ is just a FHIR server– Same query capabilities

• Point to document– Any document (FHIR Doc, CDA, PDF etc).

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XDS FHIR Style (MDS)

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When to use Documents?

• No different to CDA• Focus is on persistence• No workflow involved

– other than post/retrieve document

• Need tight rules over authenticated content• Want to communicate multiple resources with control over

how data is presented• Data spans multiple resources

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Documents

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When to avoid Documents?

• Need for workflow– Request/response, decision support

• Data is dynamic– I.e. want view of data now, not at time of authorship– Multiple contributors over time

• Resources need to be accessed/manipulated independently

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Documents

Paradigms: Messages

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Messages

• Similar to v2 and v3 messaging• Also a collection of resources as an ATOM feed• Allows request/response behavior with bundles for both

request and response– /message endpoint on REST server

• Event-driven– E.g. Send lab order, get back result

• Can be asynchronous

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Messages

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Messages – are bundles

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Observation Resource

MessageHeadersource destination

Device Resource

Patient Resource

<feed> <entry> <MessageHeader /> </entry> <entry> <Observation /> </entry> <entry> <Patient /> </entry> <entry> <Device /> </entry></feed>

event

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MessageHeader Resource

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Resource used in both request & response

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FHIR messages

• No storage of the “Message” resource implied. Might be used in a router, converted to v2, etc.

• The server can process them based on the event code and return the response as another message (again a bundle).

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Communicating messages

• Message Exchange Pattern• Synchronous in standard• Async supported• Reliability

• Transport• REST supported but, you can send FHIR Messages over mail, MLLP,

TCP, IPoAC (or Healthlink!)

• FHIR defines an HTTP end-point for messages• http://server.org/fhir/Mailbox

• Response comes back in the acknowledgment payload

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Revisiting the Immunization Forecast

TCH Forecaster FHIR ServerFHIR Client

TCH Forecasterwith FHIR Message InterfaceFHIR Client

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When to use Messaging?

• Request/response workflow• Need to drive behaviors more complex than CRUD on a

single resource– E.g. merge, complex queries

• Need for asynchronous communications• Need to communicate information about many resources

but want to minimize exchanges• No “identity” for many resources

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Messages

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When to avoid Messaging?

• Precise control required on how data gets persisted/displayed to humans

• Need for lightweight communications• Want to avoid pre-negotiations on behavior

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Messages

Paradigms: Services

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Service Oriented Architecture (SOA)

• Do whatever you like – (based on SOA principles)– Ultra complex workflows– Ultra simple workflows– Individual resources or collections (in Atom or other formats)– Use HTTP or use something else– Only constraint is that you’re passing around FHIR resources in some

shape or manner

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Services

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When to use Services?

• All previous paradigms are a type of services interface• Use a custom service when capabilities of other paradigms

don’t fit requirement– Operations other than CRUD on a resource (e.g. decision support)– Workflow more complex than simple request/response– Need to mix document persistence with

behavior

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Services

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When not to use services?

• When something else will do the job as well– I.e. Don’t define a custom service for something that already naturally

is handled by REST, messaging, etc.

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Services

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Paradigm guidance

• No absolutes– Consider a “when to avoid” as a note of caution– Capabilities/architecture of legacy will often drive approach,

particularly initially• E.g. If v2 back end, messaging

– Architectures will be driven by legacy requirements, architectural preferences, enterprise architecture commitments, etc.

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Combining paradigms

• No requirement for a system to only support one paradigm– E.g. hospital may be primarily messaging, but use documents for

discharge summaries and reports and expose registries and appointments via REST with a few custom services for decision support or specialized workflow

• Data (generally) shared easily across paradigm boundaries• Caveats:

– If updates come in via document, message or service, RESTful version id still needs to increment

– Documents should typically be persisted whole, not reconstituted from parts

• Ensures signature validity– Legacy messaging systems may not provide the metadata to easily

expose or manipulate discrete resources via REST

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Resources in more detail

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Resource Definition

• Every resource definition has:– Scope and use– ‘UML’ representtaion– XML representation– Bindings– Constraints– Resource specific notes– Examples

• And computable– XSD Schema– schematron

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XML & JSON

<Patient xmlns="http://hl7.org/fhir"> <text> <status value="generated" /> <div xmlns="http://www.w3.org/1999/xhtml">Doe, John</div> </text> <identifier> <label value="NI" /> <system value="http://moh.govt.nz/fhir/patient/nhi" /> <value value="PRP1660" /> </identifier> <name> <use value="official" /> <family value="Garrett" /> <given value="Gordon" /> </name></Patient>

{ "resourceType": "Patient", "text": { "status": "generated", "div": "<div xmlns=\"http://www.w3.org/1999/xhtml\">Doe, John</div>" }, "identifier": [ { "label": "NI", "system": "http://moh.govt.nz/fhir/patient/nhi", "value": "PRP1660" } ], "name": [ { "use": "official", "family": [ "Garrett" ], "given": [ "Gordon" ] } ]}

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Specify format using REST

GET /fhir/Patient/1?_format=json HTTP/1.1

HTTP/1.1 200 OKContent-Type: application/json+fhir;charset=utf-8Content-Length: 787

GET /fhir/Patient/1 HTTP/1.1

Accept: application/json+fhir

HTTP/1.1 200 OKContent-Type: application/json+fhir;charset=utf-8Content-Length: 787

Same for Create/Update

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Resource metadata

Patient

MRN 22234“Ewout Kramer”30-11-1972Amsterdam

Metadata

Resource Identitieshttp://fhir.hl7.org/Patient/23E455A3Bhttp://fhir.hl7.org/Patient/23E455A3B/_history/4

Last updated2013-12-23T23:33:01+01:00

http://hl7.org/fhir/tag/profilehttp://hl7.org/fhir/Profile/us-core

http://hl7.org/fhir/taghttp://example.org/fhir/Status#Test

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Identity

• 2 different ‘sorts’ of identity– ID identifies a resource on a server

• Is metadata• Will change between servers

– Identifier• Business identifier• Is an element in the resource

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A Resource’s ID

• In fact: an URL

– http://server.org/fhir/Patient/1

endpoint

resource type

identifier

Note: This URL resolves to the current version of a resourceIt’s also specific to a server

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“Business” identifiers

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Narrative

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Tags

• Contain metadata about resources– Beyond ID, version & date

• Used for different purposes:– Compliance to Profile – Security – e.g. sensitivity of resource– Indicate Document/Message– User defined

• Transported in different ways:– REST – as an HTTP header– In a bundle (document, message, transaction) - in the feed.category

element

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Versioning

• Most recent version– http://server.org/fhir/Patient/1– Returns single resource

• All versions– http://server.org/fhir/Patient/1/_history– Returns bundle of versions

• Specific version– http://server.org/fhir/Patient/1/_history/_1– Returns single resource

• Version support is optional• Works at instance and type level

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Resource Reference

Example: part of DiagnosticReport

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Coded values: the ValueSet resource

• Most coded elements have a set of possible values– Large or small – Static

• (change slowly)

• Can use ValueSet resource to define set of possibilities– A “true” FHIR ValueSet resource (may be version specific)

• Can contain:– References to a terminology (like SNOMED)– A list of specific codes

• Examples– International examples

• All the HL7 version 2 ‘tables’– NZ Examples

• Iwi & Hapu• DHB’s

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Example of ValueSet<?xml version="1.0" encoding="UTF-8"?><ValueSet xmlns="http://hl7.org/fhir"> <text> <status value="additional"/> <div xmlns="http://www.w3.org/1999/xhtml">The value set for confidentiality codes in the elbonian document sharing project. The codes are defined directly by the valueset, rather than references to an external terminology</div> </text> <name value="ConfidentialityOptions"/> <description value="ConfidentialityOptions"/> <status value="draft"/> <!-- Define the options in the resource rather than an external terminology--> <define> <system value="http://fhir.moh.elbonia.com/confidentiality"/> <concept> <code value='N'/> <display value="Normal"/> <definition value="That the document is of normal confidentiality "/> </concept> <concept> <code value='H'/> <display value="High"/> <definition value=”That the document is Highly confidential - eg Mental health "/> </concept> </define></ValueSet>

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Contained resources

• When the contained resource has no separate identity

• Has quite a few limitations• Use sparingly

– Bundle always better if possible

<Composition xmlns="http://hl7.org/fhir"> <extension>...</extension> <text>...</text> <contained> <Organization id="org1"> <!– other data --> </Organization> </contained> <information> <!-- other attributes --> <custodian> <reference value="#org1" /> </custodian> <!-- other attributes --> <information> </Document>

Bundles in more detail

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Review

• Atom as the bundling mechanism– Query results– Document– Message

• Request & Response– Batch/Transactions

• XML or JSON– Conversion routines available– (Can’t use ordinary ones)

• Use tags to identify Documents & Messages– First resource significant

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Resource Entry

Version-specific id

Resource id

Last modified

Resource content

Human-readable form,just like Resource.text

Tags

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Bundle as a serialized Object Graph

Profiles and Extensions:Profiles

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The need for Profiles

• Many different contexts in healthcare, but a single set of Resources– A desire to keep the resources manageable– Most elements in base resources optional

• Need to be able to:– Describe restrictions based on use and context– Support elements not in the core resource

• Allow for these usage statements to:– Authored in a structured manner– Published in a repository– Discoverable at Design and Run-time– Used as the basis for validation, code, report and UI generation.

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Profiling a resource. For example...

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Require that the identifier uses the NHI – and is required

Limit names to just 1 (instead of 0..*)

Limit maritalStatus to another set of codes that extends the one from HL7 international

Add an extension to support “Iwi”

Note: hardly any mandatory elements in the core spec!

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Capabilities of Profiles

• Descriptive– Information about the Profile (what, why, who)

• Extending a resource– Adding new elements– Same capabilities/datatypes as existing ones

• Constraining a resource– Specifying datatypes for an element– Modifying datatypes (eg translations)– Defining terminology bindings– Specifying multiplicity (eg make an element required)– Further refining repeating values (‘Slicing’)

• Example of Composition.section (Document)– Cannot specify default values for resource instances

• Everything explicit in an instance

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Structured & published

• A Profile is just a “normal” Resource• Any FHIR server could serve Profiles (just like Patients, Observations,

etc…)• So, any FHIR server is a profile repository!• A profile is simply referred to by its URI:

– Like any other resource• e.g. http://hl7.org/fhir/Profile/iso-21090

– Extensions in an ‘instance’ of a resource refer to the profile that defined them using the URI

– Need to think about re-usability when designing profiles

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Who publishes a Profile?

http://www.hl7.org/fhir/Profile/iso-21090

http://www.hl7org.nz/fhir/Profile/patient

http://www.health4all.org/fhir/Profile/

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Using profiles

• If we are a server then a client can read our conformance resource, which will list the profiles we support, and provide a link to them.– Conformance also has other functions like specifying supported resources,

operations on those resources & interoperability paradigms

• If we are a client, we can tell a server that we conform to a profile using a tag (the server will probably still check).– We could also ask a server just to validate– Could set up ‘distributed’ validation with (eg) National Validation servers

used by local/regional servers

• If we receive a resource with an extension we don’t recognize, it will point to the profile in which it is described so we can decide what to do with it.– Note that a single resource can reference different profiles

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What’s in a profile, and its relationships?

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Descriptive

IdentifierName, VersionPublisherDescription, CodeStatusDate (of publication)

Resource and Datatype Constraints

Extension Definition

Conformance(server)

Resource (via Tag)

ValueSetValueSet

Extension in Resource

Tag

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Scale / design

• Make a profile with just extensions• Make a profile with just 1 resource + extensions on that

resource• Make a profile with all (say national) resources + extensions.

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Profile Descriptive information

• To describe the purpose of the Profile• To help with location• Details

– Identifier: Universally unique identifier, assigned by author value=“urn:hl7.org:extensions:iso-21090“ or “2.16.840.1.113883.10.20.2.1”

– Version: Version of the profile, manually maintained by author. Suggested format: a timestamp (e.g. 2013-01-01T12:34:45)

– Name: Free natural text name (e.g. “Extensions to support Orion Medications”)– Publisher: organization or individual responsible for publishing. Should be populated (e.g. “FHIR

Project Team“)– Telecom: one or more contact points of the publisher (telephone, email, website etc)– Description: longer description of the contents of the profile– Code: one or more coded descriptions to help with finding the profile– Status (fixed choice of draft, active, retired) + experimental Y/N– Requirements: scope & usage (the “need” or “why” of the profile)– Date (of publication), e.g. “2013-07-07"

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Constraining Structures (elements)

• Defining terminology bindings– ValueSet is useful

• Specify element datatypes• Further refining repeating values (‘Slicing’)• Specifying multiplicity

From the spec

Possibilities

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Profile example

Medication.code with a defined valueset

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Profile Example

• MedicationPrescription.asNeeded required, and must be boolean

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Slicing

• Constraining an element with 0..* , 1..*• FHIR Document as an example• Composition resource is the CDA Header equivalent

– Composition.section is 0..*– A CCDA equivalent profile might specify the sections allowed

• Different document types would have a profile

Profiles and Extensions: Extensions

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Extensions

• Resources design for the 80% - Allow easy extension for the remaining 20% of elements

• Note - You’re not extending a resource per se, but you specify its characteristics and where an extension may occur:– A specific element within a resource – A specific element within a datatype– All elements referencing a datatype– All elements mapping to a specific mapping target– An extension

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(c) 2012 HL7 International

04/12/2023

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Extensions

• In FHIR, extensions are “normal”– Consequence of the 80% rule – keep the simple stuff simple– Extensions can exist anywhere

• Yes, even inside boolean or date– Conformant systems can’t reject instances just because they contain

unrecognized extensions– They could:

• Display them– Should be in resource narrative

• Store as a ‘Blob’• Make a conscious decision to ignore (unless ModifierExtension)

– (Could lookup profile)

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Extension definition

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Note: multiplecontexts!

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An Extension in a resource

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Extending a multiple birth

Key = location of formal definition

Value = value according to definition

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Modifier Extensions

• Also a core part of FHIR– Needed because some extensions can’t be safely ignored– Can’t compute on an element containing an unrecognized modifier

extension. However, can:• Reject instance• Just display narrative• Retrieve definition & seek human review

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Modifier Extension decisions

• When should you introduce them?– modifierExtension breaks interoperability so:

• If you can accomplish your objective without one, do that– Consider a new resource or Other– Could requirement be met by an element that doesn’t change other

element interpretations?– Best used when already part of existing practice, but in too narrow an

area to justify being part of core

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‘Other’ resource

• When there’s no way to extend an existing one• Has:

– Identifier– Code– Subject– Author– Created

• Rest is extensions• Should discuss with community first

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Designing a Profile

• Define Use Case • Choose resources

– ‘Other’ if you have to

• Constrain base elements– Remove– Make required– Define ValueSets and bindings

• Define extensions– Try to re-use existing if possible– Note ‘hierarchy’ of extensions:

• HL7• National• Local

• Build profile• Publish

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The need for Governance

• Profiles & extensions allow a user to customize their use of FHIR

• HL7 is establishing publically available registries– For reference purposes

• With great power...

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Profile editors

• Forge (FHIR.furore.com/forge)

Server specific notes

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Overview of a server

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HTTP / REST interface Encoding/decoding, param validation, syntax validation

Fhir Service

Indexer / Search Storage

Implement service operations as described in spec

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From wire to store

Storage

Fhir Service

REST interface

JSON/XML

POCO/POJO

DBMS

O-R Map

FHIR Parser

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JSON/XML

POCO/POJO

Serialize

FHIR Parser

NoSql(Xml/Json)

JSON/XML

POCO/POJO

DBMS

Serialize

FHIR Parser

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Conformance resource

• Allows a server to indicate:– Metadata about the server– The resources they support

• The queries against those resources– The paradigms they support

• REST, messaging, services– Specific (custom) queries– The profiles it supports

• Is a normal resource– Supports discoverability (think UDDI for SOAP)

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Conformance

• Which FHIR version?• Which resources?• Which paradigms ?• What search operations?• What formats?• What profiles?• Is this a test server?

• Who can I contact?

• Do you support History?• Do you support JSON/XML?

• Is a normal resource• Supports discoverability (think

UDDI for SOAP)

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Operation Outcome

• When something goes wrong….return the OperationOutcome Resource!

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Special endpoints

• Binary– Store/retrieve a blob.– No query

• Document– Works at ‘document’ level– Query on composition

• Mailbox– Processing endpoint– Exact actions depending on Trading Partner Agreement

• Note MessageHeader properties – eg event, reason

Workflow

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Workflow

• Resource describe ‘things’ • Workflow says what to do with those things• Eg

– ePresciption– Lab order– Referral

• Order resources– Order– OrderResponse

• Combination of Order(for workflow) and specific resource– Eg Order + MedicationPrescription

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Referrals workflow

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Security and Privacy

(Coming to the end…)

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Overview

• Signatures– On bundles

• Tags used to ‘annotate’ resources– Eg private resource, ‘Special

Patient’– Application applies policy

• Resources are atomic level• Some ‘security-related’

resources– SecurityEvent– Provenance

• Philosophically FHIR delegates security to infrastructure– Others do that better– But does have comments

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Wrapping Up: Tools for Developers

• Specification– The full specification (included build tools) can be downloaded from the CVS at:

http://gforge.hl7.org/gf/project/fhir • (Free to download, need account to update)

• Examples• Validation files

– XSD, Schematron

• Test Servers– Open source

• Reference Implementations– Java, .net, Objective-C, javascript– Open source– Reference Implementations from www.hl7.org/fhir

• Tooling– XML/JSON editor– REST client

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Further Information & Help

• Information:– Specification: www.hl7.org/fhir

• Fully hyper-linked• Includes many sample files and links to codesets & terminologies

– Wiki pages: http://wiki.hl7.org/index.php?title=FHIR– HL7 Lists server: from HL7.org– Blogs (listed on spec)

• Assistance– ‘Stack Overflow’ – tag hl7-FHIR– Skpe conversations (email me – david.hay@orionhealth.com to be

included)

Whew! Next Steps in New Zealand?

A group discussion