The SOA Magazine

It's no big secret that one of the primary influences of service-orientation has been the well established object-oriented design paradigm. Though there are distinct differences, there is also much common ground between these two design philosophies. In fact, if it wasn't for the innovative design principles and patterns formalized by objectorientation, the service-oriented architectural model and the Web services framework would not exist as they do today. This two-part article series studies object-orientation and service-orientation by providing a comparison of goals, concepts, and principles. Both articles are comprised of excerpts from the book "SOA: Principles of Service Design" [REF-1]. Note: The terms "object-oriented analysis and design" (OOAD) and "object-orientation" are used interchangeably in this article. Also, the upcoming sections contain references to service-orientation design principles that are not explained. If you are new to service-orientation, visit SOAPrinciples.com [REF-2] for introductory descripitions of each of the eight design principles. Introduction: A Tale of Two Design Paradigms Object-oriented analysis and design was responsible for popularizing the vision of building streamlined applications comprised of reusable, flexible software. Further supported by the sophisticated processes and conventions of the unified modeling language (UML) and a set of classic design patterns that changed the face of distributed application design, object-orientation evolved into a well-rounded and mature design framework. OOAD originally grew out of a need to bring order to unstructured development processes that had resulted in various problems, including the creation of the notorious spaghetti code. It drew from best practices that emerged from procedural programming approaches and combined these with a design philosophy that aimed to shape software into units that more closely mirror the real world. Object-orientation aspires to maximize the fulfillment of business requirements throughout the lifespan of an application, including its post-deployment upgrades and extensions. It provides numerous rules and guidelines that govern the careful separation of application logic and data into objects that can be individually maintained to help minimize the impact of change on the application as a whole. Many of the UML conventions and documentation techniques further provide a comprehensive means of expressing customer requirements and predictable runtime application behavior. Collectively, families of UML diagrams and specifications combined with established principles and practices help designers ensure that applications are built to be both robust and flexible. Also on the agenda for object-oriented applications is the fostering of reusable code. Key techniques, such as inheritance and polymorphism (discussed in Part II of this article series) are positioned to allow different software programs to benefit from logic already created for others. http://www.soamag.com/I15/0208-4.asp (1 of 8)09/02/2008 4:28:39 PM