From a Post on the CrossRef’s CrossTech Blog:
Do you want to see if a CrossRef DOI (typically assigned to publications) refers to DataCite DOIs (typically assigned to data)? Here you go:
http://api.labs.crossref.org/graph/doi/10.4319/lo.1997.42.1.0001
Conversely, do you want to see if a DataCite DOI refers to CrossRef DOIs? Voilà:
http://api.labs.crossref.org/graph/doi/10.1594/pangaea.185321
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About five years ago, CrossRef and DataCite explored the possibility of exposing linkages between DataCite and CrossRef DOIs. Accordingly, we spent some time trying to assemble an example corpus that would illustrate the power of interlinking these identifiers. We encountered a slight problem. We could hardly find any examples. At that time, virtually nobody cited data with DataCite DOIs and, if they did, the CrossRef system did not handle them properly. We had to sit back and wait a while.
And now the situation has changed.
This demonstrator harvests DataCite DOIs using their OAI-PMH API and links them in a graph database with CrossRef DOIs. We have exposed this functionality on the “labs” (i.e. experimental) version of our REST API as a graph resource.
MORE info and examples along with some caveats in the complete blog post.