XML database

As XML database databases or database management systems are referred to that store data in XML format or can deal with XML data otherwise. We can therefore divide the XML database systems into two categories:

  • XML - enabled: Conventional database systems ( eg, relational database systems, ...) allow the mapping to or from XML format. We call this approach as a data-oriented.
  • Native XML database systems: These systems store the information, similar to the storage of XML documents in the file system directly as XML documents from. They are therefore referred to as document- oriented.

Benefits

Due to the widespread use of XML in applications (especially web applications ) the use of XML database systems is obvious, since in this way the conversion process (eg from Relational to XML) is obsolete.

Besides this advantage brings added benefits through the XML format:

  • Since XML documents have a tree-like structure, hierarchical data structures can be particularly simply serialized. XML database systems can be used for example to store structured documents.
  • Since XML and related markup languages ​​widespread, " open standards " and the W3C are many implementations (mostly open source), these standards are available, a range of instruments to process XML is available.

Disadvantages

  • XML database systems are not as efficient as relational database systems with large data base.
  • XML database systems are often not as mature as they tend to be younger.
  • There is often a lack of experience compared to relational database systems.

Comparison of technologies and languages

What is in relational database systems (SQL to query and manipulation), is in XML databases especially XPath, XQuery, and XUpdate. The well-known from the relational database systems, foreign keys can be realized through the XPointer here. For transformation and presentation of the XML data XSL (XSLT, XSL -FO ) can be used.

Persistence

A common method for storing XML data can be performed efficiently in the XPath queries is to use a pre-post table. The nodes of the XML tree once numbered in Preorder - order ( depth-first search, document order ) and once in post-order ( breadth-first search ). The numbering can be understood as coordinates in the plane, in an XML tree is placed.

Document-oriented database Hierarchy Persistence (computer science) BaseX EXist
427
de