22. The computer-readable storage medium of claim 20 wherein: said request is for an update of said target XML node; said request includes a new node value for said target XML node; the step of creating an updated stream of XML data includes copying the new node value into the updated stream of XML data at the first offset position; and the step of copying the new node value is performed after copying data into the updated stream of XML data from the original stream of XML data starting at the beginning point in the original stream of XML data up to the first offset position; and performed before copying data into the updated stream of XML data after the new node value from the original stream of XML data starting at the second offset position up to the ending point in the original stream of XML data.
22. The computer-readable storage medium of claim 20 wherein: said request is for an update of said target XML node; said request includes a new node value for said target XML node; the step of creating an updated stream of XML data includes copying the new node value into the updated stream of XML data at the first offset position; and the step of copying the new node value is performed after copying data into the updated stream of XML data from the original stream of XML data starting at the beginning point in the original stream of XML data up to the first offset position; and performed before copying data into the updated stream of XML data after the new node value from the original stream of XML data starting at the second offset position up to the ending point in the original stream of XML data. 23. The computer-readable storage medium of claim 22 wherein the instructions further include instructions for validating the updated stream of XML data against a schema, further comprising: identifying a beginning position and an end position of a portion of the updated stream of XML data, the portion of the updated stream of XML data comprising a structure and a type; wherein the portion of the updated stream of XML data is less than all of the updated stream of XML data; recording the structure of only the portion of the updated stream of XML data; and comparing the structure of only the portion of the updated stream of XML data to a schema definition of the type of the portion of the updated stream of XML data.