During each shift in excess of five consecutive hours of work, an employee is entitled to at least a one-half hour break, except where it is unreasonable or impossible. The break can be paid, or unpaid, at the employer's discretion.
This means that where a shift is less than 5 hours in length the employer is not obliged to provide a rest period. Where the shift is longer than 5 hours (e.g. 8 or 9 hours) the obligation of the employer is to provide at least 30 minutes of break time sometime during the shift. The 30 minutes can be taken in one unbroken period but may be provided as two 15-minute or three 10-minute breaks.
This, of course, is the minimum standard, and in practice for a full day shift the amount of break time provided is frequently more than the specified minimum.