<when> Description When node is similar to the <xsl:when> instruction. It allows to test a condition and, if the condition is true, to execute a specific block of instructions. See example with choose and otherwise nodes. Attribute Summary   Name Default Value Optional Accepted Values base   true   test   false   Attribute Detail   base this is a generic block attribute that allows URI base redefinition: all uri attributes used in children nodes of this block will be relative to this new base definition (except if there is another child block node that redefines a new base). This is only a convenience attribute in order to simplify URI specifications. A base attribute must be a valid (well formed) URI, absolute or relative to another base definition. test any valid XPath expression (either absolute or relative to the current node). Children   catch, choose, depends, echo, filter, finally, foreach, if, remove, save, sax, source, template, try, variable