| One of the most significant impacts of XML is that it is turning the web into a database. The popularity and advantage of XML in the web ask for sophisticated engines to support the manipulation of the data stored in XML documents. Many approaches are being studied for XML document updates. The more traditional XML-enabled database approach extends the relational database systems with the ability to store, manage and update XML documents. Unfortunately, because the relational databases do not fully support XML data structures, the solutions proposed are incomplete and have unresolved challenges. Another approach is to use native XML tools. Even though native tools for manipulating XML documents are available, most are still in their infancy phase. This is particularly true regarding updating XML data. Even though operations for updating XML documents at the node level exist, when it comes to updating a set of elements in an XML document, the process is left at the users’ control.;This research studies the execution of a sequence of update instructions on an XML document, referred to as an “XML update transaction,” and proposes an efficient yet light-weight mechanism to make the update transaction an atomic operation. Various types of XML update transaction are defined depending on the update operations (deletes or inserts). Incremental constraint checks are automatically inserted in the update transaction to generate a safe XML update transaction, which will ensure that the transaction would commit only if it leaves the XML document valid relative to its schema. The safe XML update transactions can be executed using any XQuery engine that supports XML updates. Experiments were designed to assess the update transaction rewrite and the performance of the resulting safe XML update transactions, which shows that it takes &thetas;(n) time to execute an XML update transaction where n is the number of elements to be modified. |
