Existing Wording
The most important of the identifiers is the Unique Device Identifier (UDI), which most medical devices are required to carry and which can be used to access the Global Unique Device Identification Database (GUDID). The UDI has its own element (udi). The UDI may identify an instance of a device uniquely, or it may just identify the type of the device. A portion of the UDI - the DI part - can be extracted from the UDI when required, and used to look up information about the device through the GUDID. Where the device has an assigned UDI, the other details carried in the resource (e.g. lot, expiry date etc) SHALL be consistent with the information encoded in the UDI or registered in the GUDID.

Proposed Wording
The most important of the identifiers is the Unique Device Identifier (UDI), required by the FDA for every medical device to bear on its label (unless excepted). The UDI has 2 components – the device identifier (DI), which is assigned at the version/model level of the device and the production identifier(s)(PI) which provide the means to track a device through its manufacture, distribution and use. The DI of the UDI is submitted in a device record to the Global Unique Device Identification Database (GUDID) and is used as the primary key to access other device information. The UDI has its own element (udi). The UDI may identify an instance of a device uniquely (when the PI(s) include a serial number), or it may just identify the type of the device. A portion of the UDI - the DI part - can be extracted from the UDI when required, and used to look up information about the device through the GUDID. The UDI can be broken into its constituent parts (DI and PI(s)) by parsing rules developed by each Issuing Agency standard. Where the device has an assigned UDI, the other details carried in the resource (e.g. lot, expiry date etc) SHALL be consistent with the information encoded in the UDI string or registered in the GUDID.

Comments
Providing additional background info

Providing additional clarification - the UDI is not captured or stored in the GUDID. Only the DI is submitted; it is the primary key to all other device data elements. The GUDID doesn't store PI; the device record contains a field to indicate which production identifiers will be found on the label but does not collect the specific date or number.

Grahame's Comments
agree but need to qualify FDA bit with USA and mention other countries are adopting same