Ananalysis of Legacy Database Updatingthroughdatabase Wrapping Technologies-A Programming Technique

Abstract

This studyexaminesLegacyDatabase UpdatingthroughDatabase WrappingTechnologies–AProgramming Technique. Legacy database updating through code level programming isdirectly updating of legacy database doesn’t consider the problem of guaranteeing dataconsistency by rejecting updates that violates constraints implicitly or explicitly. By usingXMLas dataexchange format of thewrapper. Wrapper architecture based on the conversionand management of the views as the bridge from global schema to local schema of various datasources. Our wrapper has two main subsystems, dataextract subsystem and query executorsubsystem. The former is for loading data for the cache in mediator when changes more thanthreshold are detected and the latter is for answering the query from the mediator. Thearchitecture adapts to the data and schema change of the data source and could answer thequery of mediator effectively. Considering the wrapper may run in the environment withoutcontrol, the process in wrapper should be simple enough. The storage in wrapper itself shouldbe as small as possible and the storage of data source could be used.While directly updating oflegacy database doesn’t consider the problem of guaranteeing data consistency by rejectingupdates that violates constraints implicitly or explicitly. The central approach in my thesis is to address the problem of providing users andprogrammers with a wrapper able to emulate implicit structure and constrains in newapplication through Data Access Layer (Database Wrapper Schema) rather than throughapplication code.