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\begin{abstract}

Barriers in parallel languages may be used to schedule parallel
activities, control memory usage and ensure proper sequentialization
of side-effects. In this paper, we present operational semantics of
barriers in Id and pH, which are non-strict, implicitly-parallel,
functional languages extended with side-effects. The semantics are
presented as a translation from a source language with barriers into a
kernel language without barriers where the termination properties of
an expression are represented explicitly as signals using a weak
head-normal form operator (\lbx{W}) and controlled \via a strict
application operator ({\tt Sap}).  We present two versions of the
semantics --- the first uses purely data-driven, eager evaluation and
the second mixes eager evaluation with a demand-driven identifier
reference mechanism. We compare and contrast the two for their ability
to do resource management and preserve useful semantic properties.

\end{abstract}
