|Syntax and mark-up / Procedures and steps|
The importance attribute of a step is used to indicate whether an element is optional or mandatory.
The step and substep elements have an optional importance attribute, which has two valid values: optional and required. The attribute is used to indicate whether the step is optional (within a set of mandatory steps), or required (within a set of optional steps). The optional setting is more commonly used than required.
During processing to a reading format, steps with an importance attribute are typically rendered with an "Optional:" or "Required:" prefix.
Typical rendering of step with importance attribute set