can't find variable javascript error
===

So I'm trying to run a  slideshow presentation tool ,and the following code is suppose to initialize the slideshow ,but I get an error which goes like 'uncaught reference error: reveal is not defined', which I don't understand cause the code simply has to start the slideshow.
Here's the code:

			Reveal.initialize({
				// Display controls in the bottom  right corner
				controls: true,

				// Display a presentation progress bar
				progress: false,

				// Click above progress bar for quick  navigation - only works if progress is true
				progressNavigation: true,
				
				// If true; each slide will be pushed  to the browser history
				history: false,

				// Flags if mouse wheel navigation  should be enabled
				mouseWheel: true,

				// Apply a 3D roll to links on hover
				rollingLinks: true,

				// UI style
				theme: query.theme || 'default', //  default/neon

				// Transition style
				transition: query.transition ||  'concave' // default/cube/page/concave/linear(2d)
			});
			</script>

awaiting enlightenment.Thanks.