Assertion: mouse's ball | /r/HasProperty | rolled on one or more buttons
Facets:
value: on the top of the casing
type: LOCATION
Source sentences:
text: A mouse consists of a metal or plastic housing or casing, a ball that sticks out of the bottom of the casing and is rolled on a flat surface, one or more buttons on the top of the casing, and a cable that connects the mouse to the computer.