A Muslim scholar chosen to speak at President-elect Barack Obama's inaugural prayer service Wednesday is the leader of a group that federal prosecutors say has ties to terrorists. Ingrid Mattson, president of the Islamic Society of North America, is one of many religious leaders scheduled to speak at the prayer service at Washington's National Cathedral. Mattson has been the guest of honor at State Department dinners and has met with senior Pentagon officials during the Bush administration. She also spoke at a prayer service at the Democratic National Convention in Denver. Mattson, who was elected president of the society in 2006, is a professor of Islamic studies at Hartford Seminary in Hartford, Connecticut. But in 2007 and as recently as last July, federal prosecutors in Dallas filed court documents linking the Plainfield, Indiana-based Islamic society to the group Hamas, which the US considers a terrorist organization.