This book bridges the gap between the theory of scientific application development and the theory and practice of application deployment over distributed systems. It addresses this imbalance by surveying a broad range of distributed applications and understanding their main characteristics; reviewing successful systems, tools, and middleware that provide support for specific patterns; and identifying and solving primary causes of difficulty in developing and using applications in distributed systems. The book offers an integrated, coherent approach for researchers in applied distributed systems and computational science, post-graduate students, and industry practitioners.