I’m using the Linked Data dereferencing capability of doi.org to retrieve metadata for articles, given a doi.org URL. The returned RDF contains references to authors, organisations and other entities that use an id.crossref.org namespace.
When I try to dereference those URLs, I get a 503 Service Unavailable error. This is really unfortunate as I was very keen to demonstrate the power of Linked Data.
Is is this a temporary situation of has that service been deprecated? What is the status of the Linked Data services in general? (I find little to no documentation on the crossref website)
Firstly, this is something we’re well aware of, and working to improve (though I can’t give an ETA). You’re not the first to notice this. Second, although we are working on an improvement, technically it should not be a problem.
Our id.crossref.org URIs were used to allow us to use RDF URI references as identifiers for all items, allowing us to expose data in RDF format, enabling Content Negotiation on our metadata. RDF does not require that a URIs actually resolves as URLs, simply that they exist. We use these identifiers for items we have no API for, but still want to identify (such as ISSN or author names).
We do not run any APIs or services on that domain, it’s just a placeholder. The HTTP 503 literally means “there’s no service here!”.
(Note that id.crossref.org URIs are not blank nodes, as they are referenced in multiple RDF documents.)
So, whilst the behaviour technically correct, it is a little confusing. I’ll be sure to update this ticket when we have something to share.