Query triggers for XML DBMS: Efficient implementation based on shadow mechanism
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Active database systems extend functionality of traditional database systems with powerful mechanisms of triggers (or active rules) support. Triggers provide a uniform and convenient base that can be used for realization of internal DBMS functions, such as support of integrity constraints, representations, access authorization, statistics gathering, monitoring and notifications and for higher efficiency of external applications. Among representative examples of external applications that can be based on the usage of properties of active DBMS are data-intensive expert systems and workflow management systems. Today, the majority of industrial relational DBMS already support triggers, while XML DBMS, which are comparatively new, lack such functionality. Expansion of the XML DBMS application field and its usage in constructing complex application system stimulates appearance of new research works aimed at extending the functionality of XML DBMS by trigger support.
In this paper, the authors define a special type of triggers for XML DBMS—XML triggers responding to data retrieval—and propose methods for their implementation. The paper also discusses examples of applications where XML query triggers occur to be useful and gives review of existing research works in this area.
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