Super-Fast XML Wrapper Generation in DB2: A Demonstration

The XML Wrapper is a new feature of the federated database capabilities of DB2/UDB v8. It enables users and applications to issue SQL queries against XML data from a variety of sources, including files and web services. The XML Wrapper assumes hierarchical XML documents modeled as families of virtual relational tables in a federated schema, which can then be queried to extract information from the XML and combine it with data from other sources. Due to the nature of the problem, using the XML Wrapper is complex and several difficult steps must be undertaken: (i) The hierarchical schema of the source must be flattened to a relational form. (ii) Each relation of the flattened schema must be registered in DB2 as a NICKNAME – a complex virtual table definition containing several XPaths as specialized options. (iii) Each NICKNAME must be accompanied by a VIEW – again a complex structure involving join conditions. Chocolate is a tool that alleviates all three tasks: Chocolate provides several flattening strategies and an interface allowing users to modify the automatically generated target schema. Once the user is satisfied with the schema, Chocolate automatically generates the corresponding NICKNAME and VIEW definitions.