When updating a valid XML Data or Schema, an efficient yet light-weight mechanism is needed to determine if the update would invalidate the document. Towards this goal, we developed a framework called SAXE, we analyzed the constraints expressed in XML schema specifications and establish constraint rules that must be observed when a schema, or an XML data conform to a given XML Schema is altered. We then classify the rules as relevant for a given update case, that is, we show the minimal set of rules that must be checked to guarantee the safety for each given update primitive. Next, we illustrate that this set of incremental constraint checks can be specified using generic XQuery expressions composed of three components. The safe updates for the XML data has the following components (1) XML schema meta-queries to retrieve any constraint knowledge potentially relevant to the given update, (2) retrieval of specific characteristics from the to-be-modified XML, and (3) lastly an analysis of information collected about the XML schema and the affected XML document to determine validity of the update. For the safe schema alteration, the components are (1) XML schema meta-queries to retrieve relevant information (2) analysis and usage of retrieved information to update the schema (3) propagate the changes to the XML data when necessary. For proof of concept, we have established a library of these generic XQuery constraint checks for the type-related constraints. The key idea of SAXE is to rewrite each XQuery update into a safe XML Query by extending it with appropriate constraint check subqueries. This enhanced XML update query can then safely be executed using any existing XQuery engine that supports updates - thus turning any update engine automatically into an incremental constraint-check engine. In order to verify the feasibility of our approach, we have implemented a prototype system SAXE that generates safe XQuery updates. Our experimental evaluation assesses the overhead of rewriting, as well as the relative performance of our loosely-coupled incremental constraint check approach against the more traditional first-change-document and then revalidate-it approach.


Advisor: Elke A. Rundensteiner

Graduate Students:

Bintou kane
Hong Su

Undergraduate Students:

Coung Diep
Victor Chen

De Ming Guang
Jennifer Look



Bintou Kane, Hong Su, and Elke A. Rundensteiner, Consistently Updating XML Documents using Incremental Constraint Check Queries (*.ps) Workshop on Web Information and Data Management (WIDM'02), Nov. 2002. page 1- 8, 2002.

Hong Su, Bintou Kane, Victor Chen, Cuong Diep, De Ming Guan, Jennifer Look and Elke A. Rundensteiner "A Lightweight XML Constraint Check and Update Framework" (*.ps) (*.pdf)
Second International Workshop on Evolution and Change in Data Management (ECDM 2002), Tampere, Finland, Oct. 2002


            Bintou Kane, Hong Su, and Elke Rundensteiner. Consistently Updating XML Documents using Incremental Constraint Check Queries WIDM'02.(.ppt)


         Documents & Source

              Safe Data Update Query Template Models (.pdf file) 

                Source Code (.zip file) Installation Readme  Safe Data Updates Only

                Safe Schema Update Query Models (.pdf file) 

               Source Code (.zip file) Installation Readme  Safe Data And Schema Updates (new version) 


         Related Work


          Tatarinov, Ives, Alon Halevy and Daniel Weld, Updating XML, SIGMOD 2001