A list of variables to use for input, output or to hold any intermediate data or document content in the flow of mashup processing. Variables must be declared as direct children of <mashup>, <macro>, <operation> or any looping statement that can contain other EMML statements.

Variables declared in <mashup> or <operation> have a global scope and are accessible in any statement. Variables declared in <macro> or looping statements have only a statement scope. Variables must be declared explicitly or implicitly before they are used.

See also Declaring Mashup and Macro Variables and Parameters for more information and examples.