| read as "vertical line?" or what?

Context:

Background knowledge is encoded through a
constrained space of hypotheses about pos-H
sible values for the latent variables, candidate
worldstructuresthatcouldexplaintheobserved
data.Finer-grainedknowledgecomesinthe“prior
probability” (h ),thelearner’sdegreeofbeliefinP h
a specific hypothesis prior to (or independenth
of) the observations. Bayes’s rule updates priors
to “posterior probabilities” ( h|d ) conditional onP hd
the observed data :d