In the context of the CATCH research program that is currently carried out at a number of large Dutch cultural heritage institutions our ambition is to combine and exchange heterogeneous multimedia annotations between projects and institutions. As first step we designed an Annotation Meta Model: a simple but powerful RDF/OWL model mainly addressing the anchoring of annotations to segments of the many different media types used in the collections of the archives, museums and libraries involved. The model includes support for the annotation of annotations themselves, and of segments of annotation values, to be able to layer annotations and in this way enable projects to process each other's annotation data as the primary data for further annotation. On basis of AMM we designed an application programming interface for accessing annotation repositories and implemented it both as a software library and as a web service. Finally, we report on our experiences with the application of mod...