">PropertyGraph</a>.  There is a function
<TT>get(Property, g)</TT> that get property map objects from a
graph. The first argument is the property type to specify which
property you want to access and the second argument is the graph
object. A graph type must document which properties (and therefore
tags) it provides access to.  The type of the property map depends on
the type of graph and the property being mapped. A trait class is
defined that provides a generic way to deduce the property map type:
<TT>pr