The actual content of an Attachment can be conveyed directly using the data element or a URL (Uniform Resource Locator) reference can be provided. If both are provided, the reference will point to the same content as found in the data. The reference can never be reused to point to some different data (i.e. the reference is version specific). The URL reference will point to a location that resolves to actual data; some URIs (Uniform Resource Identifier). If the URL is a relative reference, it is interpreted in the same way as a resource reference.
The content type element should always be populated when an Attachment contains data and may be populated when there is a URL. It can include charset information and other mime type extensions as appropriate. If there is no character set in the content type then the correct course of action is undefined, though some media types may define a default character set and/or the correct character set may be able to be determined by inspection of the content.
Attachment data are not constrained, and therefore can be of any content type and encoding. Therefore extra care needs to be taken to validate the content against malicious or malformed content.
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.