Updating XML views published over relational databases: Towards the existence of a correct update mapping

Abstract

Abstract. Updates over virtual XML views that wrap the relational data have not been well supported by current XML data management systems. This paper studies the problem of the existence of a correct relational update translation for a given view update. First, we propose a clean extended-source theory to decide whether a translation mapping is correct. Then to answer the question of the existence of a correct mapping, we classify a view update as either un-translatable, conditionally or unconditionally translatable under a given update translation policy. We design a graph-based algorithm to classify a given update into one of the three update categories based on schema knowledge extracted from the XML view and the relational base. This now represents a practical approach that could be applied by any existing view update system in industry and in academic for analyzing the translatability of a given update statement before translation of it is attempted.

Characterising relational view updates using relative information capacity

“…There has been considerable research into this problem over the last four decades, and numerous different approaches have been suggested in the context of relational, non-relational (e.g., [21,29,31,33]), and deductive databases (e.g., [2,3,7,24]). We shall now briefly review some key developments in the relational context.…”

Updating Typical XML Views

“…This type of updates is called a view update. Because of its important use, view update has a long research history [1,9,11,12,6,4,13]. The work in [5] discusses detailed semantics of view updates in many scenarios.…”

“…View side-effect [13] occurs if the translated source update causes more-than-necessary change to the source data which leads to more-than-expected change to the view instance. View side-effect makes Equation (1) violated.…”

“…In case of updating XML views over relational databases, updates to XML views need to be translated to updates to the base relational tables. The works in [4,13] propose two different approaches to the problem. The work in [4] translates an XML view to some relational views and an update to the XML view to updates to the relational views.…”

“…It then uses the relational approach to derive updates to the base tables. The work in [13] derives a schema for the XML view and annotates the schema based on keys of relational tables and multiplicities. An algorithm is proposed to use the annotation to determine if a translation is possible and how the translation works.…”