1. NHIN DIRECT REST IMPLEMENTATION Prepared by: The NHIN Direct REST Team June 8, 2010

2. Some Definitions »REST – Representational State Transfer »Introduced in Roy Fielding’s PhD thesis in 2000 »Theory Requests and responses between clients and servers embody the transfer of “representations” of “resources” –Example: Resource is a “List of Messages”. Representations could be an XML or HTML expression of the list. Resource: Any addressable concept »Practice HTTP methods (typically GET, POST, PUT, DELETE) applied to resources expressed as URIs HTTP status codes for coarse-grained response interpretation MIME Content-Type header for request and response interpretation

3. Why REST? »Simple Knowledge of HTTP method primitives, Content-Type, and URL formation rules is all that is required »Ubiquitous HTTP is well understood with client libraries in virtually any environment and servers available for free »Proven HTTP has been the protocol of the web for years »Extensible New URL formation rules and Content-Type headers to address new resources »Scalable REST HTTP-based services scale using well-understood techniques

4. Why REST? »Integration Simplicity Low level of knowledge needed (HTTP methods, headers, and URL formation rules) »Tooling Lots of development tools to make coding simple (Spring MVC 3.0, JAX-RS, etc…) »Natural X.509 certificate directory mechanism /certs resource (more later)

5. Achievements »REST Specification http://nhindirect.org/REST+Implementation Still some debate on the best way to architect the Abstract Model status function (/status resource versus MDN) »Java-based HISP implementation (MedPlus/Quest & VisionShare) Spring MVC 3.0-based REST backbone protocol. Demonstrated HISP to HISP messaging. REST and SMTP/POP3 edge protocol support –Functioning with standard email client & REST test clients –In prototype with MedPlus Care360 EHR as Source/Destination S/MIME message-based security (sign and encrypt). TLS between HISPs /certs resource for retrieving X.509 certificates

6. Achievements »Ruby on Rails HISP implementation (Arien “private citizen” Malec) REST backbone protocol S/MIME message-based security (sign and encrypt) /certs resource for retrieving X.509 certificates »Java HISP implementation (Argonne National Labs) REST backbone protocol SAML integration

7. REST API Examples »https:// /nhin/v1/ / /messages »Dr Johnson retrieving a list of messages from his HISP: https://hisp-a.com/nhin/v1/nhin.DodgeClinic.com/DrJohnson/messages GET method Returns an Atom feed containing URIs of available messages »Dr Johnson retrieving a message from his HISP: https://hisp-a.com/nhin/v1/nhin.DodgeClinic.com/DrJohnson/messages/8dc78b1e-4aea- 46a3-8317-43fe57ac5d6c The UUID at the end of the URL is the message ID Response format is an RFC 5322 email message »HISP A posting a message sent by Dr. Johnson to Dr. Nelson https://nhin.MetroCardiology.com/nhin/v1/nhin.MetroCardiology.com/DrNelson/messages POST method RFC 5322 email message format nhin.MetroCardiology.com resolve in DNS to the IP of the HISP serving Dr. Nelson »HTTP GET the X.509 certs (as an Atom feed) for DrJohnson@nhin.DodgeClinic.com https://nhin.DodgeClinic.com/nhin/v1/nhin.DodgeClinic.com/DrJohnson/certs

8. Security & Trust »S/MIME message-based signing and encryption is used by two of the three implementations for endpoint to endpoint privacy, authentication, integrity and non-repudiation. Ruby on Rails utilizes OpenSSL Java (Spring MVC implementation) uses the nhin-d-jagent HISP-to-HISP prototyping has been achieved »Java (Spring MVC) still uses TLS for HISP to HISP on-the-wire privacy Needed to protect To and From headers (potential PHI) Still some debate about the desirability of client certificates –They would stop nefarious traffic at the network level –They may imply a global HISP circle of trust »Java (Argonne) uses SAML

9. Coding Experiences »Java (Spring MVC) »Ruby on Rails »Java (Argonne)