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From chemical abundance analysis of stars in the Sagittarius dwarf spheroidalgalaxy (Sgr), we conclude that the alpha-element deficiencies cannot be due tothe Type Ia supernova (SNIa) time-delay scenario of Tinsley (1979). Instead,the evidence points to low [alpha/Fe] ratios resulting from an initial massfunction (IMF) deficient in the highest mass stars. The critical evidence isthe 0.4 dex deficiency of [O/Fe], [Mg/Fe] and other hydrostatic elements,contrasting with the normal trend of r-process [Eu/Fe]r with [Fe/H]. Supportingevidence comes from the hydrostatic element (O, Mg, Na, Al, Cu) [X/Fe] ratios,which are inconsistent with iron added to the Milky Way (MW) disk trends. Also,the ratio of hydrostatic to explosive (Si, Ca, Ti) element abundances suggestsa relatively top-light IMF. Abundance similarities with the LMC, Fornax and IC1613, suggest that their alpha-element deficiencies also resulted from IMFslacking the most massive SNII.  For such a top-light IMF, the normal trend of r-process [Eu/Fe]r with [Fe/H],as seen in Sgr, indicates that massive Type II supernovae (>30Msun) cannot bemajor sources of r-process elements.  High [La/Y] ratios, consistent with leaky-box chemical evolution, areconfirmed but ~0.3 dex larger than theoretical AGB predictions. This may be dueto the 13C pocket mass, or a difference between MW and Sgr AGB stars. Sgr hasthe lowest [Rb/Zr] ratios known, consistent with low-mass (~2Msun) AGB starsnear [Fe/H]=-0.6, likely resulting from leaky-box chemical evolution.  The [Cu/O] trend in Sgr and the MW suggest that Cu yields increase with bothmetallicity and stellar mass, as expected from Cu production by the weaks-process in massive stars.  Finally, we present an updated hfs line list, an abundance analysis ofArcturus, and further develop our error analysis formalism.

Chemistry of the Sagittarius Dwarf Galaxy: a Top-Light IMF, Outflows and the R-Process