A Composition is a basic structure from which FHIR Documents – immutable bundles with attested narrative – are built. A single logical composition may be associated with a series of derived documents, each of which is a frozen copy of the composition.
A Composition is a structure for grouping information for purposes of persistence and attestability. There are several other grouping structures in FHIR with distinct purposes:
The List resource – enumerates a flat collection of resources and provides features for managing the collection. While a particular List instance may represent a “snapshot”, from a business process perspective, the notion of “list” is dynamic – items are added and removed over time. The List resource references other resources. Lists may be curated and have specific business meaning.
The Group resource – defines a group of specific people, animals, devices, etc. by enumerating them, or by describing qualities that group members have. The Group resource refers to other resources, possibly implicitly. Groups are intended to be acted upon or observed as a whole (e.g., performing therapy on a group, calculating risk for a group, etc.). This resource will commonly be used for public health (e.g., describing an at-risk population), clinical trials (e.g., defining a test subject pool) and similar purposes.
The Bundle resource – is an infrastructure container for a group of resources. It does not have narrative and is used to group collections of resources for transmission, persistence or processing (e.g., messages, documents, transactions, query responses, etc.). The content of bundles is typically algorithmically determined for a particular exchange or persistence purpose.
The Composition resource – defines a set of healthcare-related information that is assembled together into a single logical document that provides a single coherent statement of meaning, establishes its own context and that has clinical attestation with regard to who is making the statement. The Composition resource provides the basic structure of a FHIR document. The full content of the document is expressed using a Bundle containing the Composition and its entries.
The Composition resource organizes clinical and administrative content into sections, each of which contains a narrative, and references other resources for supporting data. The narrative content of the various sections in a Composition are supported by the resources referenced in the section entries. The complete set of content to make up a document includes the Composition resource together with various resources pointed to or indirectly connected to the Composition, all gathered together into a Bundle for transport and persistence. Resources associated with the following list of Composition references SHALL be included in the Bundle:
Other resources referred to by those resources MAY be included in the Bundle at the discretion of the authoring system as documented in the system’s operation definition (such as $document operation), or as specified by any applicable profiles.
Fast Healthcare Interoperability Resources (FHIR) is a draft standard describing data formats and elements (known as “resources”) and an application programming interface (API) for exchanging electronic health records. The standard was created by the Health Level Seven International (HL7) health-care standards organization.
Its goal is to facilitate interoperation between legacy healthcare systems, to make it easy to provide healthcare information to healthcare providers and individuals on a wide variety of devices from computers to tablets to cell phones, and to allow third-party application developers to provide medical applications which can be easily integrated into existing systems.
FHIR provides an alternative to document-centric approaches by directly exposing discrete data elements as services. For example, basic elements of healthcare like patients, admissions, diagnostic reports and medications can each be retrieved and manipulated via their own resource URLs (Uniform Resource Locators). FHIR was supported at an American Medical Informatics Association meeting by many EHR (Electronic Health Record) vendors which value its open and extensible nature.