  As the first step in a comprehensive, comparative, direct analysis of the
spectra of Type Ia supernovae (SNe Ia), we use the parameterized supernova
synthetic-spectrum code, SYNOW, to interpret 26 spectra of the well-observed SN
1994D. Our results are consistent with the traditional view that the
composition structure (element abundance fractions versus ejection velocity) is
radially stratified. We find that resonance-scattering features due to
permitted lines of Ca II, Na I, and Fe II persist to more than 100 days after
explosion. The fitting parameters for SN 1994D, together with those to be
determined for other SNe Ia, will provide an internally consistent
quantification of the spectroscopic diversity among SNe Ia, and shed light on
how the various manifestations of observational diversity are related to their
physical causes.
