I haven’t reviewed it much myself yet, but there’s a new CrossRef metadata search… with API. The API could prove useful.
Note that this is just for CrossRef-managed DOI’s — not all DOI’s use CrossRef as a registrar.
For DOI’s in general, the extent of API you have at present, I think, is (potentially) getting back metadata about a known DOI (not reverse-lookup like CrossRef metadata search). You can get some metadata back with content-negotiation for various formats on the canonical dx.doi.org endpoint, although what metadata response formats are available (if any) depends on the registrar’s implementation still. That is, initially just CrossRef, although I think I recall hearing DataCite added some metadata formats available this way, not sure if they overlap with CrossRef’s.
Back to the CrossRef metadata search with API… could it serve as a “poor man’s” embedded ‘article search’ function? Metadata-search only, not fulltext search, but that can sometimes be good enough, for instance for finding known-items with title supplied. As it will only find articles with DOI’s (CrossRef-assigned DOI’s at that), it would not be sufficient for my own needs here where I work–but if you don’t have access to and can’t afford anything else, it might be a minimally better-than-nothing option.
Also, free-form citation matching!
Looks like they also have an API for submitting a free-form citation, and getting back matches with DOI! It’s sort of a ‘holy grail’ for me to provide a service where users can paste in a free-form citation, and get to our access/delivery options. Obviously the hard part is parsing or otherwise going from that free form citation to structured data — it’s harder than you might initially think, citation formats are various and often followed more in the breach.
Of course, this service will still only work for articles with (CrossRef) DOI’s, and I haven’t tested it to see how well it works with real data, but potentially an interesting possibility.