Concordance is a tool that monitors selected projects of the workspace and maintains an index of cross-resource EMF references. Concordance can then use this index to automatically reconcile references when models are moved, and report broken references when models are updated/deleted.
Concordance is the newest part of Epsilon and its API is still volatile. We plan to have a first stable version of the API accompanied by exemplar tools in early 2010. Check back soon or drop by the forum for more details.