As XML becomes ubiquitous so the need for powerful tools to manipulate XML data becomes more pressing. Merging XML is particularly tricky, but often necessary to consolidate data feeds from heterogeneous systems, or to synchronize submissions of XML fragments which make up a larger document. An automated mechanism for defining and controlling such merges has been developed and is demonstrated to provide a consistent, adaptable and resilient solution to this problem. Integration into an information pipeline allows limitless customization.

As XML tools become more powerful and able to handle many of the peculiarities of real data, so the possibility of achieving a genuine, intelligent merge of XML data sets becomes a reality. Increasingly users are wanting to apply concurrent engineering to XML, i.e. to allow multiple users to add to a single data set simultaneously.

This paper proposes a systematic approach to merging based on the use of an intermediate XML file that contains both of the files to be merged in a formal structure that clearly identifies data that is common to both files and data that is unique to one of the files. The advantage of this intermediate file is that many of the conflicts that typically emerge when XML data is merged can be identified and resolved. The resolution of these conflicts is a key to achieving a useful merge.

The paper addresses issues of real data in terms of how to control the correct correspondence between the data within the files. Finding this correspondence is a necessary step before a sensible merge can be executed. Applying these techniques means that XML files containing libraries of data, e.g. XML Schemas or SVG files, can be intelligently merged in an automated way. This improves quality and reduces the required human effort involved in these essential processes.

The paper uses XML Schema files as an example to illustrate the merge operation and to identify areas where special care is needed.

The proposed method provides XML users with a general-purpose merge operation for the amalgamation of XML data and thus gives another reason for adopting XML as the preferred format for documents and data.