We present and compare two new techniques for learning Relational Stru
ctures (RSs) as they occur in 2D pattern and 3D object recognition. Th
ese techniques, namely, Evidence-Based Networks (EBS-NNets) and Rulegr
aphs combine techniques from computer vision with those from machine l
earning and graph matching. The EBS-NNet has the ability to generalize
pattern rules from training instances in terms of bounds on both unar
y (single part) and binary (part relation) numerical features. It also
learns the compatibilities between unary and binary feature states in
defining different pattern classes. Rulegraphs check this compatibili
ty between unary and binary rules by combining evidence theory with gr
aph theory. The two systems are tested and compared using a number of
different pattern and object recognition problems.