A common belief is that open book exams reduces cheating since all the information that a student would wish to look up is already with them. Open book exam therefore tests a person's knowledge and organization rather than memorization.
However, a textbook is not merely a set of references written by distinguished authors in size 12 fonts and high quality paper, it could also be used as a set of notes for students to scribe onto, whatever in his fancy.
This becomes highly problematic in courses where the material is often repeated year after year, such as computer science or computer hardware courses where students are not expected to remember say commands, or highly specialized mathematical formulas. In these cases, students will just jot down the solution to past term paper i.e. all the questions from 1997 - 2014, and do a compare and match when they receive their actual exam paper. After which, answers that belong to similar question will simply be jotted down. 100% accuracy with zero understanding.
This happens so frequently, I am completely confused by the very definition of an open book exam. Are students allowed to jot down notes (such as the solutions to past paper) in their textbooks in an open exam? What is considered cheating in an open text book exam??