|Syntax and mark-up / Procedures and steps|
Task topics allow two levels of steps within a single procedure: steps and substeps. Where possible, substeps should be avoided.
In DITA, procedural steps can be structured in two levels: steps and substeps. Any step within a steps block can be broken down into substeps, but a substep cannot be further broken down.
If a procedural step is broken down into substeps, the substeps section can be used within an individual step (as a child of the cmd element). In other cases, a choicetable structure, designed for decision points in a step, may be appropriate.
The substeps element contains one or more substep elements, which are almost identical to the step element.
Avoid substeps whenever possible. If a step is a task in itself, it is best approach is to document that secondary task in a separate topic, and cross-reference the task topic to the second task topic. Your task should ideally be made up of a single level of steps. Re-writing a procedure is sometimes necessary to find a way of simplifying it to one level.
If the variation between procedures is only very slight, you may be able to write a single procedure but use choices or choicetable elements to distinguish the differences.