XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (30 page)

When a sequence constructor is evaluated, the result is, in general, a sequence of items. Many instructions such as

,

, and

create new nodes; a couple of the new instructions introduced in XSLT 2.0 such as

and

can also return references to existing nodes in a source document. It is also possible for the sequence to contain atomic values: these can be produced using the

and

instructions.

Most likely, the sequence returned by a sequence constructor will be used to build the content of an element node in the result tree. In the example shown in
Figure 2-9
:

• The sequence constructors contained in the
  
  elements always (if they are evaluated at all) produce a sequence of three nodes: two empty
  

  ---

  
  elements and a text node.
  
• The sequence constructor contained in the
  
  instruction returns a sequence that is the concatenation of the nodes returned by the first
  
  instruction, then the nodes returned by the
  
  instruction, and finally the nodes returned by the second
  
  instruction. The result of the template is this sequence of nodes.
  

Suppose that the template rule in our example is invoked using a construct such as the following:

The

instruction results in the sequence of nodes produced by evaluating the selected template rule. In fact, this instruction can select several

elements, and the template rule is invoked once for each one. The resulting nodes are all concatenated into a single sequence. Because the

instruction is the only instruction in the sequence constructor contained by the