  Determinations of CKM matrix elements are clouded by uncertainties in
nonperturbative QCD parameters that relate measurable quantities to the
underlying parton-level processes. A principal goal of the CLEO-c program is to
provide precision measurements in the c-quark sector that will stimulate
lattice QCD theorists to calculate relevant nonperturbative QCD parameters in
this sector and to validate the calculations. This interaction between theory
and experiment should build confidence in calculations of the parameters in the
b-quark sector required for precision determinations of the CKM matrix elements
Vcb, Vub, and Vtd.
