An extension to the halfedge datastructure. Consisting of 
vertices V
halfedges E
half-facets F
simplices (called regions R)
facetedges , a set of tuples, each consisting of a half-facet and a half-edge

further introduction can be found here:
http://www3.math.tu-berlin.de/geometrie/wordpress/andre/?p=25

git-svn-id: https://svn.math.tu-berlin.de/svn/jtem@1350 f5b180c5-49ee-4939-b20e-b6ed35f0f7b7