If a dataset contains constraints (such as a foreign-key constraint) it is possible to cause exceptions to be thrown depending on the order of operations performed against the dataset.
Now there's evidence that antibiotics commonly prescribed to help control severe breakouts may, in a very small number of patients, lead to inflammatory bowel disease.
Thursday's incident occurred amid concern over the Pope's health prompted by a Vatican decision to schedule the mass two hours early this year instead of the traditional midnight hour.
Social issues were less sensitive: immigrants were not blamed for crime as they were in Germany, say, and Britons were not especially likely to complain about cultural clashes.
"We've been working on this problem for over 10 years and the vaccines we've tried in the past have induced some immune responses but they have not been very effective."