2.1 Introduction

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In 1999, Software AG released the first version of its native XML server Tamino, which included a native XML database. The term native has become popular since then, being used with differing meanings. While some sources (e.g., Bourret 2002) define a native XML database system only by its appearance to the user ("Defines a [logical] model for an XML document . . . and stores and retrieves documents according to that model. . . . For example, it can be built on a relational, hierarchical, or object-oriented database. . . ."), Software AG takes the definition further by requiring that a native XML database system be built and designed for the handling of XML, and not be just a database system for an arbitrary data model with an XML layer on top. At first glance, this might not make a difference at the user level, but a fundamental difference is inside the system. XML is different from other well-known data models (e.g., relational, object-oriented) in a number of aspects. As a consequence, mapping XML to another data model always causes an "impedance mismatch," leading to limitations in functionality and/or performance.

XML by itself leaves many choices for the modeling of data. Two modeling approaches are contrasted by R. Bourret: Data-centric documents have a regular structure, order typically does not matter, and mixed content does not occur. This is the type of information usually stored in a relational or object-oriented database. Document-centric documents are characterized by a less regular structure, the occurrence of mixed content, and the significance of the order of the elements in the document. Of course, all choices in between these two extremes are possible. Tamino XML Server handles these kinds of XML documents uniformly and is designed to process XML documents efficiently regardless of their structure. In addition, Tamino can store other types of data (e.g., images, HTML files, etc.) that are relevant in a Web context.

Tamino XML Server has a complete database system built in, providing transactions, security, multiuser access, scalability, and so on. In addition, Tamino is tailored to fit the needs of XML: It supports relevant XML standards and is optimized for XML processing. Tamino is available on Windows, several flavors of UNIX (including Solaris, AIX, HP-UX, Linux), and OS/390.


Part IV: Applications of XML