A unified framework for data translation over the Web

We propose a comprehensive framework for the management and the exchange of (semi) structured Web data, described according to a variety of formats and models. We consider various schema definition languages for XML (DTD, XML Schema and XDR) a model for semistructured data (OEM) and a model used to store Web data (the relational model) and show that the primitives adopted by all of them can be classified into a rather limited set of basic types. We then define, building on these basic types, a notion of "meta-formalism" that can be used to describe, in a uniform way, these heterogeneous representations of Web data. In this framework, the translation of schemes and instances between different models are based on the translations of the involved primitives. Complex translations can be then obtained by simply combining a number of predefined operations, which implement standard translations between primitives. Moreover we show that, for translating between any pair of models, it is sufficient to define a number of translations which is linear in the number of models. These results can be used to support a number of involved Web-related activities like: information exchange between different organizations, integration of data coming from heterogeneous information sources, storage of native XML data in a DBMS and publishing of existing structured (relational) data in XML.