oai is an R client to work with OAI-PMH (Open Archives Initiative Protocol for Metadata Harvesting) services, a protocol developed by the Open Archives Initiative (https://en.wikipedia.org/wiki/Open_Archives_Initiative). OAI-PMH uses XML data format transported over HTTP.
OAI-PMH Info
See the OAI-PMH V2 specification at http://www.openarchives.org/OAI/openarchivesprotocol.html
Implementation details
oai is built on xml2 and httr. In addition, we give back data.frame's whenever possible to make data comprehension, manipulation, and visualization easier. We also have functions to fetch a large directory of OAI-PMH services - it isn't exhaustive, but does contain a lot.
Paging
Instead of paging with e.g., page and per_page parameters,
OAI-PMH uses (optionally) resumptionTokens, with an optional
expiration date. These tokens can be used to continue on to the next chunk
of data, if the first request did not get to the end. Often, OAI-PMH
services limit each request to 50 records, but this may vary by provider,
I don't know for sure. The API of this package is such that we while
loop for you internally until we get all records. We may in the future
expose e.g., a limit parameter so you can say how many records
you want, but we haven't done this yet.
Acknowledgements
Michal Bojanowski contributions were supported by (Polish) National Science Center (NCN) through grant 2012/07/D/HS6/01971.