Descent theory and mapping spaces

The purpose of this paper is to develop a theory of (infinity, 1)-stacks, in the sense of Hirschowitz-Simpson's 'Descent Pour Les n-Champs', using the language of quasi-category theory and the author's local Joyal model structure. The main result is a characterization of (infinity, 1)-stacks in terms of mapping space presheaves. An important special case of this theorem gives a sufficient condition for the presheaf of quasi-categories associated to a presheaf of model categories to be a higher stack. In the final section, we apply this result to construct the higher stack of unbounded complexes associated to a ringed site.