View updates in a semantic data modelling paradigm

The Sketch Data Model (SkDM) is a new semantic modelling paradigm based on category theory (specifically on categorical universal algebra), which has been used successfully in several consultancies with major Australian companies. This paper describes the SkDM and investigates the view update problem (VUP) in the SkDM paradigm. It proposes an approach to the VUP in the SkDM, and presents a range of examples to illustrate the scope of the proposed technique. In common with previously proposed approaches, we define under what circumstances a view update can be propagated to the underlying database. Unlike many previously proposed approaches, the definition is succinct and consistent, with no ad-hoc exceptions and with the propagatable updates from a broad class. We avoid ad-hoc exceptions by basing the definition of "propagatable" on the state of the underlying database. Examples are given that demonstrate that, under a range of circumstances, a view schema can be shown to have propagatable views in all states, and thus state independence can frequently be recovered.