This looks awesome. I'll have to remember this for those situations where I am looking to embed metadata.
A document’s DOI (http://www.doi.org/ or on Wikipedia under Digital Object Identifier) is an important part of the citation of a document. Many style sheets allow for just the DOI of a paper as the citation. Because DOIs are unique they can act as URIs which are resolvable and look like URLs. However, a DOI is different than a URL for where a digital object might be located. It might be well argued that a DOI should be tracked in the metadata schemes of archives which collect language and linguistic data.