 If "A" is a quasi-coherent sheaf of algebras in an algebraic stack "X" over a scheme "S", then there is a stack Spec("A") generalizing the construction of the spectrum Spec("A") of a commutative ring "A".An object of Spec("A") is given by an "S"-scheme "T", an object "x" of "X"("T"), and a morphism of sheaves of algebras from "x"*("A") to the coordinate ring "O"("T") of "T".If "A" is a quasi-coherent sheaf of graded algebras in an algebraic stack "X" over a scheme "S", then there is a stack Proj("A") generalizing the construction of the projective scheme Proj("A") of a graded ring "A".