syntax for domain usage declaration

Is the following description correct? It's in
ArchSpec/Base/Specialization/"Domain usage declaration (the domains
attribute)". I'm having trouble making sense of it:

	Each domain defines its module ancestry as a parenthesized
	sequence of space-separated module names from root module
	to provided module: '(', modulename, (' ', modulename)+, ')'.

The example given there is

	domains="(topic ui-d) (topic sw-d) (topic pr-d cpp-d)"