CSC/ECE 517 Fall 2009/wiki2 16 tvhi

Service Oriented Architecture(SOA) and Patterns

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Introduction

         During the past decade, SOA has been one of the favorite topics among the research community. There are many techniques and services which satisfy the business requirements when implemented stand alone. The challenge is the integration of these various services into a cohesive framework and translation into methodologies so that they can be used for software development. There are potential advantages of using standardized services such as providing high level abstractions to organize large scale applications in open environments, ensuring coordination and interoperation between the programmers. Moreover, generic tools can be developed based on the standards to control the entire software life cycle from design, development, testing, and deployment to maintenance.

         Design Pattern on the other hand helps to build any system more efficiently reducing the time consumption and making the solution more generic. When it comes to common systems like banking or online admission form, it might feel like a lot of unnecessary rework where every bank has to build the system from the scratch. If there is a basic pattern that the bank could use and build its system on the top of that, it saves a lot of work. In terms of Services and Service Oriented Architecture, a design pattern could fall in any level of SOA architecture like business, application etc. Services can be developed using the different patterns available as protocols or APIs. In SOA, when designing a particular service, understanding these patterns can be a lot of help especially in the standardization of service. Any generic web service that has to be implemented can be mapped to one or more of these design patterns. Hence a thorough understanding of these patterns is essential before proceeding with the design of the services

Terminology

• Service Oriented Architecture -

• Design Patterns -

Traditional Design Patterns

         The book [1] is considered to be the bible of Design Patterns. Not only is one of the oldest material on Design Patterns but the patterns described act as the baseline to the next generation patterns which are derived from them. Here is a brief list of all the traditional design patterns.

Similarities and Differences

         As discussed in the previous section, the traditional design patterns as described in 1 cover all the major templates that are needed to design any system. Similarly, design patterns used for SOA cover all the templates required to design any service. Hence we can consider the traditional design patterns to be a superset of the SOA patterns. The SOA patterns are called Architectural Patterns which comprise of all the design patterns for the overall composition of a service based solution as discussed in 2. Although most of the design patterns for SOA are derived from the traditional structural and behavioral patterns, there are some subtle differences between them.

         Patterns like service discovery patterns and service interaction patterns are very specific to SOA or the service that is under the limelight. However, messaging patterns and workflow patterns can be used while designing any system while defining their process. The workflow pattern is derived from the traditional behavioral patterns. It is a combination of many behavioral patterns. However, workflow patterns are specific to the service also. It depends on the domain under question. For example, if we are designing a system that enables physics researchers to run their experiments online and analyse the data, then the workflow could be a combination of one or many templates (which again could be the one or more of which could be used to construct a workflow for chemists running the experiments. We can consider a workflow pattern to be a combination of Adapter, Facade and Controller patterns.

         At a microscopic level, trying to spot the dissimilarities between the traditional and SOA design patterns would be unjust because the SOA patterns are derived from the traditional ones. SOA patterns are more specific to web services while the traditional ones can be considered as the primitive patterns which can be used and customized to create patterns specific to a domain.