[show abstract][hide abstract] ABSTRACT: A major problem in today's information-driven world is that sharing heterogeneous, semantically rich data is incredibly difficult. Piazza is a peer data management system that enables sharing heterogeneous data in a distributed and scalable way. Piazza assumes the participants to be interested in sharing data, and willing to define pairwise mappings between their schemas. Then, users formulate queries over their preferred schema, and a query answering system expands recursively any mappings relevant to the query, retrieving data from other peers. In this paper, we provide a brief overview of the Piazza project including our work on developing mapping languages and query reformulation algorithms, assisting the users in defining mappings, indexing, and enforcing access control over shared data.
[show abstract][hide abstract] ABSTRACT: This paper discusses an approach to exporting relational data in XML format for data exchange over the web. We describe the first real-world application of SilkRoute, a middleware program that dynamically converts existing relational data to a user-defined XML DTD. The application, called XBrain, wraps SilkRoute in a Java Server Pages framework, thus permitting a web-based XQuery interface to a legacy relational database. The application is demonstrated as a query interface to the University of Washington Brain Project's Language Map Experiment Management System, which is used to manage data about language organization in the brain.
[show abstract][hide abstract] ABSTRACT: XML is the "lingua franca" for data exchange between inter-enterprise applications. In this work, we describe SilkRoute, a framework for publishing relational data in XML. In SilkRoute, relational data is published in three steps. First, the relational tables are presented to the database administrator in a canonical XML view. Second, the database administrator defines in the XQuery query language a public, virtual XML view over the canonical XML view. Third, an application formulates an XQuery query over the public view. SilkRoute composes the application query with the public-view query, translates the result into SQL, executes this on the relational engine, and assembles the resulting tuple streams into an XML document. This work makes two key contributions to XML query processing. First, it describes an al-gorithm that translates an XQuery expression into SQL. The translation depends on a query representation that separates the structure of the output XML document from the computation that produces the document's content. The second contribution addresses the optimization prob-lem of how to decompose an XML view over a relational database into an optimal set of SQL queries. We define formally the optimization problem, describe the search space, and propose a greedy, cost-based optimization algorithm, which obtains its cost estimates from the relational engine. Experiments confirm that the algorithm produces queries that are nearly optimal.