h these requirements are not
explicitly stated, they are statically checked during compilation and
failure to meet them yields compile-time errors.</p>
<p>Although the static typing of property map interfaces usually provides
desirable compile-time safety, some algorithms require a more dynamic
interface to property maps. For example, the Boost Graph Library (BGL)
provides functions that can initialize a graph by interpreting the
contents of a textual graph description (i.e. a GraphML file).  Such
general-p