Xslt Generate-id Function And Key

The <xsl:key> element declares a named key — that is, a name-value pair assigned to a specified element in an XML document. The key is used with the key() function in XPath expressions to help you access the assigned elements in a complex XML document efficiently.

Attributes

Oct 03, 2001  XSLT's generate-id function generates a unique ID for a node passed to it as an argument. This ID starts with a letter so that you can use it as the value of an XML ID attribute. This ID starts with a letter so that you can use it as the value of an XML ID attribute. XSLT keys provide a simple and efficient way of looking up values based on other values. First, we will take a look at the syntax of keys and then we will look at how they are used in practice.

• name
  Specifies the Qualified Names of the key.

Xslt Generate-id Function And Key Code

• match
  Specifies the Patterns that identifies a node that holds this key.

• use
  Specifies an Expressions to be used as the value of the key. The key value can be one of the following: an attribute, a child element, or the content of the matched element.

Element Information

Xslt Generate-id Function And Key Number

Remarks

You can use keys as generalized IDs for referencing elements in an XML document. To do this, first use <xsl:key> to declare a key for a node. Then call the key() function to retrieve the node, supplying the name and value of the key as the function arguments,. For more information, see the example below.

Xslt Document Function Examples

Multiple keys can be declared on a node. This provides multiple ways to query a node.

When you work with relatively large XML documents, a key is often a fast wayto query elements. This is because it essentially indexes the locations of the desired nodes ahead of time. However, when <xsl:key> elements are compiled, the XSLT processor will not create such indexes unless a key() function is called against the keys. This ensures that the time-intensive indexing operation is performed only when it is necessary.

In a stylesheet, <xsl:key> elements are top-level elements, and cannot appear within a template. To avoid circular references, you cannot use parameter or variable references as part of an <xsl:key> match.

Example

Xsl Function List

The following topic provides an example of the <xsl:key> element.