⇒ Using RDFa to Annotate Images
### The Idea
⇒ Scientific Measurements in Schema.org
The physical sciences use the idea of a [quantity](http://en.wikipedia.org/wiki/Quantity#Quantity_in_physical_science) to measure the world around us. While that might seem simple, basing a measurement on a system of units that can be quantified, measured accurately, verified isn't exactly simple. Nevertheless, a great deal of time and effort has converged into the [International System of Units (SI)](http://en.wikipedia.org/wiki/International_System_of_Units) .