An array design consists of design element groups as well as information about element zone layout. Physical array design has been made as a subclass of array design, to allow "virtual" array designs with element groups but no zone layout information; such "virtual" designs can be used, e.g., to define different reporter-composite sequence mappings for the same physical array design. Zones can be grouped together to form zone groups; zones within the same zone group would have the same spacing between them, whereas zones from different zone groups can have different spacing. Zones/zone groups sometimes are referred to as blocks/metablocks.