1. ARCHITECTURE OVERVIEW
I’d like to take you on a brief tour of the architecture of SMART. First, let’s establish a common vocabulary, so that we can have a base for understanding the main components of SMART.
ARCHITECTURE OVERVIEW

2. Vocabulary Apps API Containers
The first component of the SMART universe is the ecosystem of SMART apps created by various software developers eager to bring solutions in the hands of clinicians and patients. The apps could include a medication manager, a diabetes evaluation suite, or perhaps a lab results visualizer. These meaningful apps could be distributed via an app store.
Then we have the containers which play the role of data providers in the SMART world. The containers could be personally controlled health records systems, electronic medical records systems, health data exchanges, or other providers. Either way a container is responsible for exposing the SMART API to the apps and providing a context in which the apps could run.
Finally, we have the interface which enables the apps and containers to talk to each other – the SMART application programming interface (or API). The API is what keeps the apps and the containers decoupled from each other allowing the users to mix and match.
Also, the API enables the substitutability of the SMART apps and containers. From the perspective of an app the containers are substitutable, because they all expose the same interface and the app can run on any one of them. Also from the perspective of the container, the apps are substitutable. The container administrator is free to pick the apps that he needs. And when a better app comes along, he can replace the existing app with the new one.
The last point that I want to make here is that in order to keep things simple, an app runs against one container at a time. The container, however, is free to connect to multiple data sources and aggregate data as needed.
API
Containers

3. SMART Components
Now let’s take a look at the SMART architecture components. At the bottom of the diagram we have the frond end of the container and the smart application within a web browser window. The container and the app might also have back end server components. For the container the back end component might be an EMR system housing a large collection of medical records. The app could have a back end that helps with elaborate visualizations, data mashing, or other complex computations.
On front end components use an interface called SMART Connect to communicate with each other right inside the browser environment. Using it the app can get patient context from the container and execute API calls. The back end components can also talk to each other. And for that they use an interface called SMART REST. Should an app choose to use the SMART REST interface, it simply has to obtain an authentication token from the container using SMART Connect, and pass it to the back end component, which can then use it to issue SMART REST calls to the container’s back end.
So, there we have it. Front end, back end, SMART connect, and SMART REST.
One thing that I’d like to point out is that the SMART API has been inspired by successful web APIs that support applications, such as Facebook , OpenSocial, and Google. What makes all of these APIs successful is that they are based on web standards such as HTTP, HTML, JavaScript, and REST. These standards allow the apps to run on separate severs against different implementation stacks.

4. Apps need
UI Standards-based integration, flexibility Authentication In-browser, server-to-server Data Context, Medical Record Elements
Now, let’s look at the elements that an app needs in order to provide a meaningful service to the end user. First, the app needs a flexible, standards-based UI that enables the user to interact with it. Next, the app needs to have an authentication mechanism with the container to establish thrust. And last but not least, the app needs data in order to work with. The data includes patient and provide context information, as well as medical record elements such as medications and lab results. We will look at each one of these components in more details.

5. Container UI
This diagram illustrates the container’s UI component in a browser window. The white portion of the screen is the UI that the container provides, which allow the user for instance to choose a patient and launch various SMART applications on his data. The main portion of the screen real estate is taken by the SMART app. The app is launched by the container in an IFRAME. An IFRAME is an in-browser mechanism that enables multiple web pages to open up on the same screen. When launched the app establishes a channel to the container using the SMART connect JavaScript library. It can then issue SMART API calls such as GET MEDICATINS in order to obtain data from the container. Finally, the app displays the data to the user and allows him to interact with it.

6. Authentication
Each container implements a consistent mechanism for delegating access: OAuth. The app only needs to speak OAuth.
The next architectural piece is the authentication mechanism. Different EMR systems have their own authentication schemas. In order to keep the app agnostic to them, it is the container’s responsibility to provide a standard way for establishing trust. And for that SMART uses oAuth, which is an open web standard for authentication. Thus the app does not have to deal with the underlying system’s permissions schema. All it needs is to speak OAuth. The container uses his internal logic to decide what the app can see and what is forbidden.

7. SMART data 80/20 approach concentrate on common outpatient data
Consistent coding systems
Medications: RxNorm (SCD, SBD, Packs)
Problems: SNOMED CT
Labs: LOINC
Extensible representations in RDF
The last component of the architecture is the medical data. And for that SMART takes what we call an “80/20” approach. What this means is that we try to pick the 20% of the fields out there that represent 80% of the data about the patients. This selectivity of SMART is one thing that makes writing SMART apps relatively easy. Also, SMART uses consistent best-of-the-breed coding systems for representing medical facts within the SMART data models. For example for medications we use RXNORM, for problems we use SNOMED, and labs are based on LOINC. The SMART data payloads are expressed in RDF and are extensible.

8. Architecture Summary SMART Containers supply Apps with UI integration
Authenticated API Access
Data
Containers shoulder significant responsibility!
Data models are critical to enable app developers
Keeping developer experience in mind
Data need to be predictable, (relatively) simple