The Digital Public Library of America (DPLA) offers a single interface that lets users search for digital content across many different institutions. Since the search must work with many different metadata sets coming from many different sources, interoperability (“the ability of multiple systems with different hardware and software platforms, data structures, and interfaces to exchange data with minimal loss of content and functionality”) becomes a truly crucial issue. This article describes ways the DPLA achieves the interoperability needed to function, especially through the use of service hubs.

DPLA links to content from two types of entities: content hubs and service hubs. Content hubs are really large organizations – including the New York Public Library and HathiTrust – which by themselves each submit 200,000 or more items. But if organizations with fewer items want to participate, they have to band together in a group to form a service hub. The service hub helps to standardize and enhance the metadata from the organizations that make it up, ensuring that it is easier for them to be accepted into DPLA. Another important way that DPLA is able to make these many different records interoperable is through use of the metadata application profile (MAP). This is a set of metadata elements pulled from many of the commonly used schemas, meaning that the DPLA can understand how these different schema elements relate to each other.

The article traced how a set of institutions in Missouri set about creating a service hub and being harvested for the DPLA. Since succeeding, they have donated over 41,557 items to the DPLA. The members think the benefits conferred by inclusion (particularly an increased number of views of their digital collections) outweigh the costs and problems of getting to that point.

Right off the bat, the article taught me much more about the DPLA (I’d only visited it briefly before – it’s really neat). But it also discussed really practical ways to address interoperability problems, both through the MAP and service hubs. I’m sure these would be good options to think about if I ever have to deal with interoperability issues myself in the future.