Institutional document repositories show a systematic growth as well as a sustainable deployment. Therefore, they represent the current backbone of a distributed repository infrastructure. Many developments for electronic publishing through digital repositories are heading in the direction of innovative value-added services such as citation analysis or annotation systems. A rich service-layer based on machine-to-machine communication between value-added services and document repositories requires a reliable operation and data management within each repository. Aggregating search services such as OAISTER and BASE provide good results. But in order to provide good quality they also have to overcome heterogeneity by normalizing many of the data they receive and build specific profiles for sometimes even one individual repository. Since much of the normalization is done at the side of the service provider, it often remains unclear — maybe sometimes also to the manager of a local repository — exactly which data and services are exposed to the public. Here, an exploratory validation method for testing specification compliance in repositories is presented.