The topic tag starts a topic page or section. A topic page or section is not linked to an identifier in some unit: it exists by itself. It must be inside a package or module tag. It must have a name attribute (for cross-referencing). If it appears inside a package, it can be nested: a topic may be inside another topic tag.
<module name="CRT"> <topic name="UsingKeyboard"> <short>Using the keyboard functions</short> <descr> To use the keyboard functions of the CRT unit, one... </descr> </topic>