International Institute was the setting Saturday at 4:30 p.m. for the wedding of Cassandra Ann Trace and Andrew Guthrie, who exchanged vows before Edward O'Keefe and Romella Hart-O'Keefe of Church of the Beloved preceding a reception. James Trace of Holyoke, Mass., and Jacqueline Trace of Buffalo are the bride's parents. Richard Guthrie of New Baltimore and Barbara Guthrie of Schenectady are the bridegroom's parents. After a trip to Sedona, Ariz., the couple will be at home in Port Chester. A graduate of Mount Holyoke College with a master's degree in library science from University at Buffalo, the bride is a librarian in White Plains Public Library. The bridegroom, a Cornell University graduate, is a manager in the tax compliance division of Ernst & Young, Manhattan.