DARIAH (Digital Research Infrastructure for the Arts and Humanities) is part of the European Strategy on Research Infrastructures. Among 38 projects originally on this roadmap, DARIAH is one of two projects addressing social sciences and humanities. According to its self-conception and its political mandate DARIAH has the mission to enhance and support digitally-enabled research across the humanities and arts. DARIAH aims to develop and maintain an infrastructure in support of ICT-based research practices. One main distinguishing aspect of DARIAH is that it is not focusing on one application domain but especially addresses the support of interdisciplinary research in the humanities and arts. The present paper first gives an overview on DARIAH as a whole and then focuses on the important aspect of technical, syntactic and semantic interoperability. Important aspects in this respect are metadata registries and crosswalk definitions allowing for meaningful cross-collection and inter-collection services and analysis.