Lisa Gregory and Stephanie Williams have published "On Being a Hub: Some Details behind Providing Metadata for the Digital Public Library of America" in D-Lib Magazine.
Here's an excerpt:
After years of planning, the Digital Public Library of America (DPLA) launched in 2013. Institutions from around the United States contribute to the DPLA through regional "service hubs," entities that aggregate digital collections metadata for harvest by the DPLA. The North Carolina Digital Heritage Center has been one of these service hubs since the end of 2013. This article describes the technological side of being a service hub for the DPLA, from choosing metadata requirements and reviewing software, to the workflow used each month when providing hundreds of metadata feeds for DPLA harvest. The authors hope it will be of interest to those pursuing metadata aggregation, whether for the DPLA or for other purposes.