CX-DIFF: a change detection algorithm for XML content and change visualization for WebVigiL

The World Wide Web is an omni-present and ever-expanding source of data. The exponential increase of information on the web has affected the manner in which it is accessed, disseminated and delivered. The emphasis has shifted from mere viewing of information to efficient retrieval and monitoring of selective changes to information content. Hence, an effective monitoring system for change detection and notification based on user-profile is needed. WebVigiL is a general-purpose, active capability-based information monitoring and notification system for HTML and XML documents. It handles specification, management, and propagation of customized changes as requested by a user. A novel aspect of WebVigiL is its ability to detect customized changes on the content of the document. This paper deals with change detection to XML documents, and change visualization in WebVigiL. The ordered tree property of an XML document is exploited for change detection. In this paper, we propose an algorithm to handle customized change detection to the contents of XML documents based on user-intent. In addition, an optimization to this algorithm is presented that has a better performance with certain desired characteristics. We also discuss various change visualization schemes to display the changes computed by WebVigiL. We highlight the change presentation in WebVigiL and briefly describe the rest of the system.