Abstract

Introduction The Web is emerging as a universal data repository, offering access to sources whose data organization varies from strictly structured databases to almost completely unstructured pages, and everything in between. Consequently, much research has recently focused on data integration and data translation systems [10, 6, 9, 8, 17, 13, 2, 19], whose goals are to allow applications to utilize data from many sources, with possibly widely varying formats. These research efforts have established a common data model of semistructured data, for uniformly representing data from any source. Recently, however, it is being realized that having a common schema model is also beneficial, and even necessary, in translation and integration systems to support tasks such as query formulation, decomposition and optimization, or declarative specification of data translation. As an example, which we use for motivation throughout the paper, recently suggested tools for data translation [2, 11, 19

Citations