  This paper explicates the direct empirical significance (DES) of symmetries
in gauge theory, with comparisons to classical mechanics. Given a physical
system composed of subsystems, such significance is to be awarded to physical
differences of the composite system that arise from symmetries acting solely on
its subsystems. So my overarching main question is: can DES be associated to
the local gauge symmetries, acting solely on subsystems? In local gauge
theories, any quantity with physical significance must be a gauge-invariant
quantity. To attack the question of DES from this gauge-invariant angle, we
require a split of the state into its physical and its representational
content: a split that is relative to a representational convention, or a
gauge-fixing. Using this method, we propose a rigorous definition of DES, valid
for any state. This definition fills the gaps in influential previous
construals of DES. In particular, Wallace's need to specialize to `generic'
states is explained and dispensed with.
