Linear types, approximation, and topology

We enrich the *-autonomous category of complete lattices and maps preserving all suprema with the important concept of approximation by specifying a *-autonomous full subcategory LFS of linear FS-lattices. This is the greatest *-autonomous full subcategory of linked bicontinuous lattices. The modalities !() and ?() mediate a duality between the upper and lower powerdomains. The distributive objects in LFS give rise to the compact closed *-autonomous full subcategory CD of completely distributive lattices. We characterise algebraic objects in LFS by forbidden substructures `a la Plotkin´