Heading levels and ditamaps

The topic hierarchy in the ditamap is used to generate heading levels and styles in page layout outputs.

In DITA, each topic is written as a standalone chunk of content. The style in which a topic title, for example, is eventually presented to the user is determined by the position of the topic in the relevant ditamap.

For example, if a topic called "About SD Cards" is located at:
Camera Model 700 > Storing Pictures > Memory > About SD Cards
then its heading style in RTF output might be Heading 4.
If that same topic is re-used in a different ditamap, located at:
Taking Pictures > Storing > About SD Cards
then its heading style in RTF output might be Heading 3. The topic is identical, but its presentation is appropriate to the output context.

And it gets better! Topic titles can be different in different ditamaps.