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Native XML Programming

XQuery is a language designed for integrating data from multiple sources, including XML sources like documents or web messages and databases. It does this by leveraging the ability of XML to model virtually any kind of data. To query anything with XQuery, it must be presented as though it were XML, either by serializing it as XML or by creating an XML view of the data through some form of middleware. For relational data, most systems use the SQL/XML mappings for the XML view, since they are quite suitable and have been specified in detail.

XML is the basis of XQuery's type system and data model. The fundamental types of XQuery include the kinds of nodes found in XML documents: document nodes, elements, attributes, processing instructions, comments, and text nodes. XQuery also supports the XML Schema datatypes for representing integers, strings, dates, and other datatypes - these built-in datatypes are predefined in XQuery, and are available with or without a schema.

Most modern programming languages provide some form of complex user-defined types, such as structures or objects. In XQuery, the only complex types are XML documents, elements, attributes, and W3C XML Schema complex types. There is no need to write a schema to create and manipulate complex XML structures in XQuery. However, if a query needs to ensure consistent use of the types in a schema, a schema may be imported into a query. This has an effect analogous to importing structure or class definitions in an object oriented language.

Programs tend to revolve around data, and the complex datatypes used in a language have a profound effect on the way that a language is used. As a result, languages are sometimes identified by the way they represent complex data; for instance, there are object-oriented languages and relational query languages. In this sense, XQuery can be considered Native XML Programming Language. XSLT and XPath are also Native XML Programming Languages. Most other languages used to process XML, including Java, C#, Perl, and Python are not. SQL/XML is fundamentally an extension to a relational query language, providing a bridge to XML.

The concept of a Native XML Programming Language is new, and many XML programmers are used to thinking of XML in terms of the constructs used in the languages with which they process XML. On XML-related mailing lists it is reasonably common to see beginners assert that XML is fundamentally relational or object-oriented, and even sophisticated XML programmers have been known to assert that XML is just text. In fact, the phrase "XML is Unicode with pointy brackets" has come to identify a vocal part of the XML community.