Synchronizing Xpath views

Abstract

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Achieving adaptivity for OLAP-XML federations

“…Furthermore, if the same information is available in the new document, only with a different schema, it may be possible to automatically identify the original information by inferring how the new schema relates to the old one. The issues related to replaced documents and schema changes are discussed further in another paper [8]. In this section, we concentrate on the situation where an XML component exhibits poor performance or, as a special case, becomes completely inaccessible.…”

“…Schema changes are handled by the View Synchronizer [8]. When schema changes are explicitly notified by the XML component, this information is handled directly by the View Synchronizer, which then updates the metadata.…”

“…Schema changes can be top-down, i.e., by modifications to the federated schema (also known as the integration schema [10]), or bottom-up, i.e., by modifications to the component schemas. Top-down schema changes are discussed in Section 6, while bottom-up schema changes are treated in another paper [8].…”

“…When schema changes are explicitly notified by the XML component, this information is handled directly by the View Synchronizer, which then updates the metadata. When changes are not explicitly notified, the detection of schema changes is performed by the XML Component Interface by assessing the validity of the returned result [8]. The View Synchronizer then tries to determine the new view query based on earlier versions of data found in the cache.…”

Achieving adaptivity for OLAP-XML federations

“…Generally, all the external data may have to be fetched each time it is used, but other strategies are also possible, such as letting the data source inform about changes to its data. Handling schema changes, e.g., updating view definitions over external XML to reflect the new structure, is a considerable challenge in itself and is treated in another paper [8]. Finally, XML data will often be retrieved from unreliable data sources such as on the Internet, which will frequently cause interruptions in the use of external data.…”