A follow up question to your articles about how to fill out Identifiers:
Typical to a software development, we take unique ids very seriously, so when you say Identifiers have to be globally unique, and also indicate that you can put the internal system patient id (for example) in the extension part of the id, i have the following questions:
1) Why would anyone outside of your system care about the patient id that is unique to your system?
2) For the document level Id, assuming your system outputs CCDs, is it the case that for patient X, every time you create a CCD for that patient the document ID should be the same? Or should it be different with each instance of the CCD that is created, such that two CCD documents should NEVER have the same ID, even if it’s the same patient.
3) Can you just plug in a non-registered UUID (universally unique ID) into every place one an ID is required and call it good? Or is it better practice(or industry standard) to go get a registered OID (or UUID) and create some kind of hierarchical numbering scheme in the document.
- Well, the answer to why someone outside your system would care about your own patient Id depends on how closely their system is bound to yours. If they receive a stream of documents, then they are interested in your patient identifier to help match previous documents in some kind of EMPI algorithm. But let’s assume the least coupled case: they are randomly encountering this document in an XDS repository for some region to which your system is only one of many (1000s maybe) that contribute documents. In this case, a target system itself is not going to make anything of your source id – but it will probably display that to the user, so that if the user chooses to contact a source clinician about the document, they can offer them a patient id. It can also be used by system administrators to debug problems. Both of these use cases are small but real.
- Every time you create a CCD (or any CDA document) for a patient, the document ID must be different. Even if you re-issue the same document with a minor amendment, the id must be different: two CCD documents should NEVER have the same ID (it is the primary key for the document on any document indexing system)
- You can plug in a non-registered UUID in most places where an ID is required. The exception is codes that you are putting in your document. Any place you use a codeSystem attribute, whatever goes in there should be registered (and OIDs are more polite than UUIDs, but not required). But for any other ID in the document, registration is not required. However it’s polite and useful to register it anyway