Experimental data (BioAssayData) can be clustered, obtaining one or more top level clusters. Each cluster consists of nodes, where each node in turn can contain subnodes (in the case of hierarchical clustering). A node can be characterized by its values (e.g., some metric of cluster quality), and a node groups together design elements (e.g., spots, genes) or bioassays (i.e., experimental conditions). BioAssayDimension is just an ordered list of bioassays, and DesignElementDimension is an ordered list of design elements.