by: Amos (Kippi) Bordowitz

The healthcare industry has long struggled with data interoperability, with systems across hospitals, clinics, and other healthcare settings often using different formats, making the transfer and sharing of data a challenge. The Fast Healthcare Interoperability Resources (FHIR) standard was introduced by HL7 to solve this critical issue, providing a modern, flexible, and efficient way to manage healthcare data. While the term “resources” is commonly used to describe the fundamental units of the FHIR data model, the true power of FHIR lies in its use of RESTful architecture, along with standardized data formats like JSON and XML. In this post, we’ll explore these key components of FHIR, examining how they make healthcare data exchange not only possible but also scalable and future-proof.

 What is FHIR?

Just in case you somehow stumbled onto our website, and are still unfamiliar, FHIR (pronounced “fire”) is a standard for exchanging healthcare information electronically. Developed by Health Level Seven International (HL7), it is designed to be flexible enough to accommodate the wide range of systems used in healthcare, from electronic health records (EHRs) to apps and wearable devices. FHIR builds upon previous HL7 standards (like HL7 v2 and HL7 v3) but is designed for a modern, internet-based environment. One of its most significant features is the adoption of a RESTful API model, which greatly enhances its usability and scalability. Read more about FHIR here.

The Role of RESTful Architecture in FHIR

At the core of FHIR’s interoperability success is its use of RESTful architecture. REST (Representational State Transfer) is a design principle used in web services that allows for easy communication between systems over HTTP/HTTPS. REST is highly scalable, stateless, and supports the use of standard HTTP operations such as GET, POST, PUT, and DELETE. This makes it a perfect fit for the healthcare industry, where systems need to communicate efficiently without complex state management.

 Why REST?

One of the reasons RESTful architecture is so beneficial in healthcare is that it enables flexibility and simplicity. REST uses standard web protocols and leverages the same methods you would use when interacting with a website. For example, in a FHIR-based system, querying for patient information is as simple as issuing an HTTP GET request, much like accessing a web page. Here’s a typical example of such a request:

GET /Patient/12345

 In this request, “Patient” represents the resource type, and “12345” is the unique identifier of the patient being queried. The server responds with the requested patient data, usually formatted in either JSON or XML. The simplicity of using HTTP methods like GET, PUT (to update resources), POST (to create resources), and DELETE (to remove resources) mirrors common web development patterns, making FHIR easier to implement and understand.

 Additionally, RESTful APIs are stateless, meaning each request from a client to a server must contain all the information needed to understand and process the request. This helps FHIR APIs scale efficiently because the server does not need to store the client’s state between requests.

REST and Resource Interactions

 In the context of FHIR, each resource type has its own endpoint and can be created/manipulated/deleted using RESTful principles. For instance, to interact with resources such as patients, encounters, or medications, the FHIR API uses well-defined HTTP methods to perform actions like retrieving or updating data. This structure allows developers to quickly build healthcare applications that can interact seamlessly with other systems following the same FHIR standard.

 The following interactions can be performed on FHIR resources through standard HTTP commands such as POST,PUT,DELETE etc.:

 – **Search:** Retrieve a collection of resources based on specific criteria.

– **Read:** Retrieve a specific resource by its unique identifier.

– **Create:** Add a new resource to the system.

– **Update:** Modify an existing resource.

– **Delete:** Remove a resource from the system.

 For example, to create a new patient record, a POST request could be made to the server, with the patient’s details formatted in JSON or XML. This modular interaction with resources simplifies application development, while enabling healthcare providers to access and exchange data efficiently.

The Importance of JSON and XML in FHIR

 While RESTful architecture handles the interaction between different systems, the data being transferred is often formatted in either JSON (JavaScript Object Notation) or XML (Extensible Markup Language). These formats are crucial to the FHIR data model as they ensure the data being exchanged is machine-readable and universally understood, regardless of the platform.

 JSON in FHIR

JSON has become the de facto data format for transmitting data in web applications due to its lightweight structure and ease of use. One of JSON’s key advantages is that it is natively supported by many modern programming languages, including JavaScript, Python, and Ruby, making it easy to integrate into web services. JSON uses a simple key-value structure that is easy to parse and understand, which is especially important when dealing with healthcare data that needs to be exchanged between diverse systems. If you are not familiar with JSON, here is a short primer.

Here’s a typical example of a FHIR resource represented in JSON:

JSON structure represents a patient resource with fields such as the patient’s name, gender, and birthdate. The lightweight nature of JSON allows it to be transferred quickly over networks, making it ideal for real-time applications in healthcare, such as retrieving patient records during an emergency.

XML in FHIR

 Though JSON is widely used, XML is also a critical format in FHIR, particularly in legacy systems that still rely heavily on XML-based data exchange. XML is a more verbose format compared to JSON but provides a more rigid schema structure, which can be beneficial in environments where strict validation and data consistency are required.

A FHIR resource represented in XML might look like this:

While XML can be more complex to work with due to its verbosity, it offers benefits like stronger validation and a well-established ecosystem in enterprise environments. This makes it especially useful in settings where backward compatibility with older systems is required.

Advantages of Using JSON and XML in FHIR

Both JSON and XML have their strengths in the FHIR data model. JSON’s simplicity makes it perfect for modern web applications, mobile apps, and lightweight APIs. Its readability, smaller size, and ease of parsing make it ideal for real-time data exchange, such as when clinicians access patient records during a consultation.

On the other hand, XML’s robustness and compatibility with older healthcare systems make it valuable in environments where data validation and strict schema adherence are critical. Its structure is better suited for systems that need to ensure the integrity of complex healthcare data or where backward compatibility with older standards like HL7 v3 is essential.

How FHIR Bridges the Gap Between Modern
and Legacy Systems

One of FHIR’s major strengths is its ability to bridge the gap between modern, cloud-based healthcare applications and legacy systems. By supporting both JSON and XML, FHIR ensures that healthcare organizations can adopt new technologies at their own pace without disrupting their existing systems.

The use of RESTful APIs and standardized data formats makes FHIR a future-proof solution. New healthcare applications can be developed quickly using FHIR’s modular approach, and existing systems can integrate seamlessly using familiar formats like XML. This adaptability allows healthcare providers to modernize their systems incrementally, avoiding costly and disruptive overhauls.

Conclusion

 FHIR is transforming the way
healthcare data is exchanged, making it easier, faster, and more efficient to share information between systems. While the concept of “resources” is fundamental to FHIR’s data model, its real power comes from its use of RESTful architecture and standardized data formats like JSON and XML. REST’s simplicity and scalability, combined with the flexibility of JSON and XML, allow FHIR to meet the needs of both modern web applications and legacy systems, ensuring seamless interoperability across the healthcare ecosystem.

As the healthcare industry continues to evolve, FHIR’s role will only become more critical. Its modular, web-based design ensures that it can adapt to new technologies and innovations, positioning it as the foundation for future healthcare interoperability solutions.

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