In many cases, the data warehouse is focused on capturing the original transaction inputs and using them as the source of data, rather than waiting for an extract or a query from the production system. This transaction capture capability has been growing in importance with the increased interest in realtime data warehouses. A serendipitous side effect of the growing use of XML is that the transaction flow from a data input terminal to the production system can be siphoned off so that the data warehouse receives the transactions in parallel with the production system. If the data is expressed in XML and the XML schemas are shared, then the data warehouse can update in parallel with the production system, without waiting for a conventional extract. One of the more interesting points of overlap between XML and relational databases is the possibility of storing XML documents directly as relations.
Direct storage can take a couple of forms.
Or relational systems will implement a new XML native data type. Vendors are discussing hybrid scenarios in which data in XML form could be joined inside the database directly to data in conventional relational tables. An XML data type in a relational system would open up whole new classes of hierarchical applications. Agnostic front-end information delivery. The widespread deployment of XML will be the final step in removing query and reporting tools from end users' machines.