OCLC exposes Work Identifiers
OCLC has extended the xOCLCNUM API to include the OCLC work identifiers (OWIs) in addition to OCLC record identifiers (OCNs) that correspond to manifestations. For several years now, WorldCat has been organised according to the FRBR model that allows grouping of various editions of publications (e.g. reprints, translations, performances, digitized copies) into works. Sometimes users require particular manifestations and sometimes not, so it is desirable to cater for both needs by allowing navigation from works to manifestations and vice versa.
The expanded xOCLCNUM service now returns variant manifestation level identifiers (OCN, ISBN and LCCN) and the OWI. In addition to starting with an OCN, ISBN or LCCN as an entry point into the API, OWI is now permitted as a starting point. For details and examples, see the xOCLCNUM web service documentation page .
Systems using the service are able to expand displays using the identifiers returned in the API: for example, the API could be called behind a button labeled "find alternative editions". The service could also be used by systems wishing to cluster search results by work, though performance requirements may preclude the option for clustering larger result sets on the fly. In anticipation of this, OCLC has a prototype service to complement the API that provides a machine readable table of OCN and OWI specific to a catalogue's subset of WorldCat. The OCN / OWI identifier combination is important as a means of linking records for particular resources as they occur in multiple databases. Only 30% of resources in WorldCat have an international identifier such as ISBN, and a recent study has shown that this applies to recently published materials as well as those published before international identifiers came into being in the second half of the 20th century. For example, in between 1970 and 1990, there are on average 9 million records per decade without international identifiers. OCLC is continuing to evolve its identifier services and encouraging adoption of its identifiers by external databases. In this way the identifiers can be used for navigating among web databases, without necessarily passing via OCLC, acting as a linchpin for mash-ups.