2017-08-07: rel="canonical" does not mean what you think it means
The rel="identifier" draft has been submitted to the IETF. Some of the feedback we've received via Twitter and email are variations of 'why don't you use rel="canonical" to link to the DOI?' We discussed this in our original blog post about rel="identifier" , but in fairness that post discussed a great deal of things and through updates and comments it has become quite lengthy. The short answer is that rel="canonical" handles cases where there are two or more URIs for a single resource (AKA " URI aliases "), whereas rel="identifier" specifies relationships between multiple resources. Having two or more URIs for the same resource is also known as " DUST: different URLs, similar text ". This is common place with SEO and catalogs (see the 2009 Google blog post and help center article about rel="canonical"). RFC 6596 gives abstract examples, but below we will examine real world e