Universal record identifier

A universal record identifier, or URI, uniquely points to a data record. It is similar in structure to a website URL, and usually has the following format: http://acmehealthcare.com/patient/nRJA4oMMLVA1UltryPiB

In this example, the issuing entity, Acme Healthcare is declared first, followed by the type of record—here, this record is for a patient. Finally, there is an identifier for the record, nRJA4oMMLVA1UltryPiB, which is unique to the Acme Healthcare system.

Since the patient identifier is unique within the Acme Healthcare system, and only one acmehealthcare.com exists worldwide, the complete URI is globally unique—hence universal.

Traditionally, URIs have been generated by centrally managed, always-online systems. In such systems, the server can easily ensure that two different URIs do not “collide”, i.e. they are unique. For example, servers can use timestamps as an input to an algorithm, and the serial nature of time ensures that the resultant URI is unique.

However, offline-capable mobile apps are increasingly being used in public health initiatives. When a new record is created using such apps, URIs need to be assigned locally, on a distributed basis. In such systems, suitable algorithms have to be deployed to reduce the risk of URI collision, while being computationally efficient. Contemporary algorithms such as xxhash reduce this risk to one in ten million or lower.