7.4 eXist-db (exist-db.org)
eXist-db is an open-source XML database and development platform. Though its purpose is not information archiving, it’s ability to store, index and easily search a large collection of XML documents makes it a good candidate for this task.
eXist-db uses XML across all layers - from data storage to the presentation layer. It provides an application development framework that uses HTML with simple templating, combined with XQuery for the application logic.
If the structure of the stored aggregated XML data doesn’t need much modification and transformation, creating an application for searching archived data can be just a matter of writing templates for viewing the data and simple XQueries to search them and, based on the required search and filtering criteria, defining indexes on the archived XMLs.