Query
Q1	Find all problems of a single patient
Q2	Find all problems of all patients
Q3	Find initial date, resolution date and severity
	of a single problem of a single patient
Q4	Find initial date, resolution date and severity
	of all problems problem of a single patient
Q5	Find initial date, resolution date and severity
	of all problems problem of all patients
Q6	Find all patients with problem 'pharyngitis',
	initial date >= '16/10/2007', resolution date
	<= '06/05/2008' and severity 'high'