Enterprise logic consists of both business and application logic. Business logic is an implementation of the business requirements and includes an organization's business processes. These requirements include things such as constraints, dependencies, pre-conditions, and post-conditions.
Application logic is the implementation of business logic in a technology solution. Application logic might be implemented in a purchased solution, a custom developed solution, or some combination of the two. The development team works to design and develop the application logic. Topics such as performance requirements, security constraints, and vendor dependencies are considered in the technical solution.
Service-orientation is related to business and application logic because a SOA is a way to represent, execute, and share that logic. Service-orientation principles can be applied to both business and application logic.
The role of services is to realize the concepts and principles introduced by service-orientation. A service layer in a software architecture is typically placed between the business and application layers. This allows services to represent business logic and abstract application logic. Just as different applications within an organization's application layer can be implemented in different technologies, services within the service layers can also be implemented in different technologies.
Abstraction is one of the important characteristics of an SOA and it enables other key characteristics, such as organizational agility. Abstraction is critical because abstracting business and application logic allows for a service-oriented solution with loosely coupled services. Achieving the appropriate level of abstraction is not a trivial task, but it can be accomplished with a dedicated team. By creating layers of abstraction, or service layers, the team can figure out how services should represent application and business logic, and how to best promote agility.
During service modeling, it becomes apparent that there are some common types of services. These types are service models, which can be used to classify candidate services. Those candidate services can then be grouped together based on their service model into a service layer.
The three common service models (and layers) are task service, entity service, and utility service:
