In a DITA task topic, steps and substeps are organized hierarchically to provide clear and structured instructions for performing a specific task. This organization ensures that users can follow the procedure systematically and understand the sequence of actions required. Steps represent the main actions, while substeps provide additional details or options within those actions.

Steps are the primary actions or tasks that users need to perform to accomplish the goal of the task. They are typically represented as numbered or bulleted items, making them easy to follow. Each step should be concise and focus on a single action. Steps can also contain substeps if further clarification or additional instructions are needed.

Substeps are nested within steps and provide detailed guidance or options for completing a particular action. They are indented beneath their parent steps and are often labeled with lowercase letters (a, b, c) or numbers (1, 2, 3). Substeps are used when a step requires multiple related actions, conditions, or choices. They break down the main step into smaller, manageable components.

Example:

        <task>
            <title>Assembling a Bookshelf</title>
            <taskbody>
                <steps>
                    <step>Unpack the bookshelf components.</step>
                    <step>Identify the following parts:
                        <substeps>
                            <substep>Two side panels (A and B)</substep>
                            <substep>Four shelves (1, 2, 3, and 4)</substep>
                            <substep>Hardware kit (screws and bolts)</substep>
                        </substeps>
                    </step>
                    <step>Attach side panel A to side panel B using screws (provided in the hardware kit).</step>
                    <step>Attach the shelves to the assembled side panels:
                        <substeps>
                            <substep>Insert shelf 1 between the top notches of side panels A and B.</substep>
                            <substep>Repeat the process for shelves 2, 3, and 4, aligning them with the remaining notches.</substep>
                        </substeps>
                    </step>
                    <step>Tighten all screws and bolts securely.</step>
                    <step>Stabilize the bookshelf by attaching the included wall anchor using a drill.</step>
                </steps>
            </taskbody>
        </task>
    

In this example:

• The <steps> element contains a sequence of steps.
• Step 2 has <substeps> nested within it to provide details about identifying components.
• Step 4 has substeps to guide the user in placing the shelves correctly.
• Substeps are used to break down complex actions into smaller, manageable parts, enhancing the clarity and usability of the instructions.