  Using the quantum two-body system as a familiar model, this talk will
describe how entanglement can be used to select preferred observables for
interrogating a physical system. The symmetries and dynamics of the quantum
two-body system provide a backdrop for testing the relativity of entanglement
with respect to observable-induced tensor product structures. We believe this
exploration leads us to a general statement: the physically-meaningful
observable subalgebras are the ones that minimize entanglement in typical
states.
