answer: age of the protagonists.
dubliners is a collection of fifteen short stories by james joyce, published in 1914. they tell the stories of the irish middle class in and around dublin in the early years of the 20th century.
joyce divides the collection into three sections dealing with childhood, adolescence and maturity. therefore, one pattern he uses to organize his stories is the age of the protagonists. the initial stories deal with children, and as the stories continue, they focus on progressively older people.