XML databases are designed to store and query large volumes of XML data.
Structured information retrieval or XML-IR is the application of information retrieval concepts and techniques to search structured data, usually in the form of documents in XML format.
Wenn wir mittendrin stecken und es nicht wahrhaben wollen? Viele glauben ja, dass die ersten grauen Haare ein Anzeichen sein können.
Die so ungeliebten kleinen Fältchen sollen auch ein Indiz sein.
However, once updates are involved, variable-length surrogates are often considered the better choice, mainly as a straightforward implementation of structural XML updates using fixed-length surrogates faces two performance bottlenecks: (i) high physical cost (the preorder ranks of all nodes following the update position must be modified—on average 50% of the document), and (ii) low transaction concurrency (updating the size of all ancestor nodes causes lock contention on the document root).
AB - Relational XQuery processors aim at leveraging mature relational DBMS query processing technology to provide scalability and efficiency.
In Proceedings of the 10th International Conference on Extending Database Technology (EDBT 2006). To achieve this goal, various storage schemes have been proposed to encode the tree structure of XML documents in flat relational tables. Basically, two classes can be identified: (1) encodings using fixed-length surrogates, like the preorder ranks in the pre/post encoding  or the equivalent pre/size/level encoding , and (2) encodings using variable-length surrogates, like, e.g., ORDPATH  or P-PBi Tree . Relational XQuery processors aim at leveraging mature relational DBMS query processing technology to provide scalability and efficiency.To achieve this goal, various storage schemes have been proposed to encode the tree structure of XML documents in flat relational tables.