This statement filters the content of a variable based on a condition and places the result in a new variable. You can also simply update the input variable with filtered results.

This returns a document with only those nodes in the input variable that match the condition. If no nodes match, the result is an empty document, typically just the root node.

The filter condition is defined in an XPath expression. You can use comparisons, position, XPath functions and dynamic expressions in the condition. You can also combine multiple conditions.

For examples, see <filter> Basics, Filtering Variables with Namespaces, Filtering Comparisons Using Variables or Presto Attributes, Filtering Based on Position, Using XPath Functions or Other Comparison Operations in Filtering, Combining Filter Criteria or Using Dynamic Filtering Expressions. See also Working Samples for information on sample mashups using this statement.