Propagating Updates Through XML Views Using Lineage Tracing

We address the problem of updating XML views over relational data by translating view updates expressed in the XQuery update facility to embedded SQL updates. Although our XML views may be defined using the full extent of the XQuery syntax, they can only connect relational tables through restricted one-to-many relationships that do not cause view side effects for a wide range of XQuery updates. Our approach is to use lineage tracing to propagate the necessary information about the origins of updatable data pieces through the query and the view code, to be used when these pieces are to be updated. Our system performs a compile-time analysis, based on polymorphic type inference and type usage, to detect the exclusive data sources, which are the table columns from the database that can be updated without causing side-effects to the view. The rest of the updates are associated with an update context in the form of a chain of tuples, which reflects the navigation path that was used to reach the update destination. At commit time, our system collectively considers all the compatible chains of all updates in the transaction and tries to relink them to new chains from the existing database whose tuples contain the updated data, so that the updates are reflected correctly without causing side effects to the other components of the view.