1. One or more device-readable media having a data structure, comprising: a first data field including a first index and a first element, the first element including a first token representing a location associated with the first index; one or more data fields including an index and an element, the element including a token corresponding to a location associated with the first index; and a second index derived from a data row, the second index related to the corresponding index of each of the one or more data fields.