Pascal Bou Nassar Youakim Badr Frédérique Biennier Kablan Barbar Extended BPEL with heterogeneous authentication mechanisms in service ecosystems. 126-133 2009 MEDES http://doi.acm.org/10.1145/1643823.1643847 conf/medes/2009 db/conf/medes/medes2009.html#NassarBBB09