  We note that the definition of diffractive events is a matter of convention.
We discuss two possible `definitions': one based on unitarity and the other on
Large Rapidity Gaps (LRG) or Pomeron exchange. LRG can also arise from
fluctuations and we quantify this effect and some of the related uncertainties.
We find care must be taken in extracting the Pomeron contribution from LRG
events. We show that long-range correlations in multiplicities can arise from
the same multi-Pomeron diagrams that are responsible for LRG events, and
explain how early LHC data can illuminate our understanding of `soft'
interactions.
