The majority of repository aggregation systems focus on the essential problem of aggregating resources for the purposes of providing cross-‐repository metadata search. While search is an essential component of an OA infrastructure, connecting and tying OA repositories together offers far more possibilities. Aggregations should not become just large searchable metadata silos, they should offer (or enable others to offer) a wide range of value-‐added services targeting all different types of users participating in the research process, i.e. not just users searching for individual publications, but, for example, those who need statistical information about collections of publications and their dynamics or those who need access to raw data for the purposes of research or applications development. These characteristics should distinguish OA aggregation systems from major academic search engines, such as Google Scholar or Microsoft Academic Search. [..] ..these systems provide only very limited support for those wanting to build new tools on top of them, for those who need flexible access to the indexed content and consequently also for those who need to use the content for analytical purposes. In addition, they do not distinguish between Open Access and subscription based content, which makes them unsuitable for realising the above mentioned vision of connected OARs.