#include <boost/graph/adjacency_list.hpp>
#include <boost/property_map/property_map.hpp>
#include <boost/graph/graphml.hpp>
#include <iostream>

using namespace std;

typedef boost::adjacency_list<> graph_t;

int main(int,char**)
{
  string empty_string;
  boost::ref_property_map<
    graph_t::vertex_descriptor,
    string
  > pmap(empty_string);
  graph_t g;
  
  add_vertex(g);
  
  boost::dynamic_properties props;
  props.property("foo",pmap);
  
  boost::write_graphml(cout,g,props);
}