Database and XML
For such cases, you might want to consider a specialised XML database, instead of transforming back- and-forth from XML, like SQL Server and Oracle. An XML database stores data natively in XML. XML format can offer the following benefits:
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The speed of your application have to be increased as all of the components in your application need to deal with the data in XML format. The XML database will eliminate the need to transform the data back-and-forth – it starts in XML, and stays in XML.
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Many of the XML databases coming out provide functionality to query the database using XPath queries, just as relational databases today use SQL. Since XML is hierarchical in nature, XPath can provide a more natural query language than SQL, which is a more focused relational database.
There are already a number of such XML databases available. The features and focus of each product can vary greatly, meaning that not all of these products are in direct competition with each other. Some of the XML databases that you may encounter include: •
Extensible Information Server, from eXcelon (http://www.exceloncorp.com)
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GoXML, from XML Global (http://www.xmlglobal.com/prod/db/) dbXML, an open source product from dbXML Group (http://www.dbxml.com)
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Tamino XML Database, from Software AG (http://www.softwareag.com/tamino/)
2.14 STORAGE OF XML DATA When it comes to storing XML there are a number of options available to us. We can store it in: •
plain flat files (such as plain text files held on the operating system’s native file system),
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a relational database (such as Oracle, SQL Server or DB2),
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an object database (which stores DOM representations of the document), and
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a directory service (such as Novell NDS or Microsoft Active Directory).
The first two options are by far the most common. If we use flat files they tend to be accessed from the file system of the operating system we are running. It is just like holding a collection of text documents or word processing documents on our file server. The important thing to do if, we take this approach is to make sure that we have a good naming convention for our files so that they are easily accessed. Relational databases, however, are still by far the most common data storage format. There are many ways to store XML data in relational databases. One, XML data can be stored as strings in a relational database. Second, relations can represent XML data as tree. Third, XML data can be mapped to relations in the same way that E-R schemes are mapped to relational schemas. Increasingly, relational database vendors are adding more sophisticated XML support to their RDBMS so that users can store data in relational tables, but simply send the database XML for it to insert, update or delete the information it holds; they can also request that contents of the database be retrieved and output in XML format. It is no longer necessary with many databases to convert the XML into another form before the database can accept it − if we are able to just send the database an XML file this will save us doing the conversion ourself.
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