Duality construction of moduli spaces

The duality of moduli spaces of coherent sheaves on curves and surfaces gives a GIT free construction of these spaces. It is a suitable generalization for topics as: strange duality, jumping lines of vector bundles on projective space, and Faltings' construction of the moduli space of semistable vector bundles on a complex curve given in his article 'Stable G-bundles and projective connections'. Using this duality we propose a construction for the moduli space of semistable sheaves on a surface.