: Many model management tasks, e.g., schema matching or merging, require the manual handling of metadata. Given the diversity of metadata, its many different representations and modes of manipulation, meta-model- and task-specific editors usually have to be created from scratch with a considerable investment in time and effort. To ease the creation of custom-tailored editing facilities, we present GEM, a generic editor capable of visualizing and editing arbitrary metadata in an integrated manner. GEM provides a stylesheet language based on graph transformations to customize both, the mode of visualization and the available manipulation operations. 1 The importance of metadata The vision of generic model management spurred by the works of Bernstein et al. [BHP00, MRB03] aims at reducing the effort to create metadata-intensive applications by defining generic operators that work on entire models and providing a model management system that implements these operators. Metadata-intensive...