  It is a common misconception that spacetime discreteness necessarily implies
a violation of local Lorentz invariance. In fact, in the causal set approach to
quantum gravity, Lorentz invariance follows from the specific implementation of
the discreteness hypothesis. However, this comes at the cost of locality. In
particular, it is difficult to define a "local" region in a manifoldlike causal
set, i.e., one that corresponds to an approximately flat spacetime region.
Following up on suggestions from previous work, we bridge this lacuna by
proposing a definition of locality based on the abundance of m-element
order-intervals as a function of m in a causal set. We obtain analytic
expressions for the expectation value of this function for an ensemble of
causal set that faithfully embeds into an Alexandrov interval in d-dimensional
Minkowski spacetime and use it to define local regions in a manifoldlike causal
set. We use this to argue that evidence of local regions is a necessary
condition for manifoldlikeness in a causal set. This in addition provides a new
continuum dimension estimator. We perform extensive simulations which support
our claims.
