We review multilevel hierarchies under two special aspects: their potential for abstraction and for storing discrete representations.
Motivated by claims to ‘bridge the representational gap between image and model features’ and by the growing importance of
topological properties we discuss several extensions to dual graph pyramids and to topological maps: structural simplification
should preserve important topological properties and content abstraction could be guided by an external knowledge base.
This work was supported by the Austrian Science Foundation under grants P14445- MAT and P14662-INF.