Metadata aggregation at GovData.de

A key challenge for open data portals is the aggregation of metadata from various data catalogs (on different administrative level or from different application felds) also known as metadata harvesting. This paper describes harvesting at the pilot of the German open government portal GovData.de, which is scheduled to become the data portal for all German public administration levels. At the launch of the pilot portal in February, eleven federal, state and local data catalogs were integrated, which produced about 2,000 open data sets. In the meantime, the number of data sets increased to over 3,100 mainly due to improved harvesting capabilities of the portal. This paper dis-cusses GovData.de metadata schema and experiences with the different harvesting techniques that are in use at GovData.de: CKAN-Harvest, CKAN-API, CSW-Harvest and JSON-Dump.