Australian Category Seminar

Fibrations and universal translations

Bob Rosebrugh·18 August 2010

Solving the "view update problem" for database updates interpreted as processes requires what have been called "translations". From this perspective, the view update problem can be seen as a lifting problem. Thus it is not surprising that fibrations play a role.

We have studied view definitions with "lens" structure, They are essentially projections and do provide translations. When C = Cat a lens G:S→V is an opfibration. On the other hand, taking the projection (G,1_V) → V from the comma category is the functor part of a monad on Cat/V. An algebra for (-,1_V) (an opfibration) provides a good notion of a generalized lens. Furthermore, an opfibration has "universal translations". These provide a universal solution to the view updating problem when G = W*:Mod(E) → Mod(V) for a view (sketch morphism) W:V→E in the Sketch Data Model.

Joint work with Michael Johnson and Richard Wood.

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