XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (511 page)

• element()
  matches any element node. This can also be written as
  element(*)
  .
  
• attribute()
  matches any attribute node. This can also be written as
  attribute(*)
  .
  

Now things start to get more complicated, because the other kinds of
KindTest
are concerned with testing for specific types of node as defined in a schema. In general, you will use these
KindTests
only to match nodes in documents that have been validated against a schema.

KindTests for Element Nodes

Let's look first at the options for matching element nodes:

• element(QName)
  matches any element node whose name is the given
  QName
  . As a pattern, this is exactly the same as writing the
  QName
  on its own. (The reason for providing this syntax is that a
  KindTest
  is allowed in contexts other than patterns; for example, in the
  as
  attribute of an
  
  element.)
  
• schema-element(QName)
  is used to test for an element that matches a top-level element declaration in the schema identified by the given
  QName
  . It's an error to use this form unless you have imported a schema containing this top-level element declaration. For example, if you write
  schema-element(mfg:invoice)
  , then the schema for the
  mfg
  namespace must have been imported, and must include a top-level element declaration of the form
  xs:element name=“invoice”
  .
  

  The element is considered to match if two conditions are satisfied:
  

  • Its name is either the same as the
    QName
    , or the name of an element defined in the schema to be a member of the substitution group with the named element as its head.
    
  • The type of the element node, identified from its type annotation, matches the type defined for this element declaration in the schema. This rule is there because a schema can allow the same name to be used in different contexts with different type definitions.
    
• element(*, QName)
  is used to test for an element whose type annotation indicates that it has been successfully validated against the schema-defined type definition identified by the
  QName
  . The
  QName
  can identify a built-in type such as
  xs:dateTime
  , or a type (which may be a simple type or a complex type) that is the subject of a named type definition in an imported schema. The test will match any element that has a type annotation that refers to the named type, or a type derived from the named type by restriction or by extension.