Data type: URI : Universal_resource_identifier

Description of: URI : Universal_resource_identifier

The universal resource identifier is defined and maintained outside HL7 by the IETF and W3C. In HL7 the URI is used to refer to addresses of communicating entities used in order to transmit any kind of information. This may be used for HL7 messaging addresses, but is also used for non-HL7 communication and non-computer communication. Designated applications are clearly: (a) Web servers (HTTP), (b) File Transfer Protocol servers (FTP), (c) Telephone numbers, (d) Telefax numbers, (e) Dialup Modem connections.

Rationale: The data type used for phone contacts and other telecommunication addresses (e.g., e-mail, web-pages, FAX, etc.) was called Technical Instance Locator. It was very similar to an Internet and W3C standard Universal Resource Locator/Identifier. That is, it consisted of two parts: a protocol descriptor and an address.

The TIL was designed as a wrapper around standard URIs in order to have the freedom to add additional protocols used in healthcare but not necessarily on the wide Internet. We feared that a direct reliance on Internet protocols might require difficult negotiations with IETF/W3C working groups before HL7 could use important extensions. Especially at the time the TIL was designed, we were not aware of a URI scheme for phone and FAX numbers – an absolutely necessary requirement for HL7.

We now learned that a URI scheme for telephone/FAX/data-modem is in a solid IETF Internet draft status, so HL7 can use this work directly. We further learned that the definition of URI schemes is not regulated by a difficult negotiation process, so that HL7 could add additional URI schemes easily as needed. We therefore concluded that relying directly on Internet standard URIs is feasible and sufficient for HL7, while being (of course) much simpler to use for HL7 implementers