We describe an algorithm for extracting form features, like protrusions or depressions on a face, through-holes or handles, from a relational boundary model of a solid object, called the Symmetric Boundary Graph (SBG). The method is based on loop identification and connected component labeling on the SBG and produces a decomposition of the object boundary into volumetric components describing features. Such a decomposition is represented as a directed labeled multigraph, called the Object Decomposition Graph.