Any Visual Welder™ system consists of a set of parts, interconnected via a network of relationships.
Starting with the "root" or "application" part, each part contains any number of holders. The holders are simply empty sockets into which other parts may be inserted; these other parts may, in turn, contain further holders, making a theoretically infinite recursive structure. The sum of these parts is the complete system; the complexity comes from how the parts themselves function internally, as described in detail in the section on parts.