Methods and systems which can be used to create data for one or more nodes of a tree data structure by searching through another data structure containing, for example, metadata that describes digital assets such as apps available through an app store. The rolling elements and the sprags make contact with respective raceway surfaces and are respectively housed in circumferentially spaced pockets formed in a common cage configured by mutually engaging and integrating two annular members in an axial direction. The received signal may be demodulated based on the empirically determined reliability values. The second end is free to move within the channel. The plating head further comprises a voltage sensor pair capable of sensing a voltage present between the plating head and the surface of the wafer, and a controller capable of receiving data from the voltage sensor pair.