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What should a Native XML Programming Language do?

A Native XML Programming Language must provide the fundamental operations needed for XML. Some of these operations are required because of the structure of XML itself.

A Native XML Programming Language should be able to easily find anything in an XML structure. XQuery, like XSLT, uses XPath for this purpose. Every XPath expression is also an XQuery expression. For instance, if the variable $cust is bound to a Customers element that contains the rows of a relational table, represented using the SQL/XML mappings, then the following path expression finds all the CustIds from that table:

A Native XML Programming Language should be able to easily create any XML structure. XQuery uses the syntax of XML for this purpose. For instance, the following XQuery expression creates a Customer element:

When XQuery uses the syntax of XML, a curly brace escapes to the syntax of XQuery, allowing dynamic expressions to be inserted. Here is an example that creates a customer with a new unique identifier:

A Native XML Programming Language should be able to easily combine and restructure information from XML sources, operating at the logical level without requiring the programmer to think about the internal representation of the XML. For instance, if we are operating on the SQL/XML views of the customers database, the following XQuery combines customers and projects to show the name of a customer and all projects associated with that customer:

A Native XML Programming Language should be able to easily use XML data in expressions. For instance, arithmetic operations should be able to work directly with XML content, observing the data types of typed data and converting appropriately when they encounter untyped data. It should be able to leverage schemas that have been imported into a query, but work well on XML structures for which no schema has been imported.

In short, a Native XML Programming Language should be able to work with XML the way XML users think of it, easily performing the kinds of tasks that XML users need to have done. XQuery attempts to do just that, based on the usage scenarios we gathered in XML Query Use Cases.