How do you classify services into different types and levels of granularity in SOA?

1 Step 1: Define the business domain

The first step is to define the business domain that you want to model with services. This involves identifying the key business processes, activities, and actors that are relevant to your domain. You can use techniques such as business process modeling, use case analysis, or domain-driven design to capture the business domain. For example, suppose you want to model a travel booking system. You might identify the following business processes: search for flights, book a flight, check-in, and cancel a booking. You might also identify the following actors: traveler, travel agent, airline, and airport.

2 Step 2: Identify potential services

The next step is to identify potential services that can support the business processes and activities that you defined in the previous step. You can use techniques such as service-oriented analysis, service discovery, or service decomposition to identify potential services. For example, based on the travel booking domain, you might identify the following potential services: flight search service, flight booking service, check-in service, and cancellation service.

3 Step 3: Classify services by granularity

The third step is to classify the potential services by their granularity, which refers to the level of detail and complexity of a service. Granularity can affect the reusability, maintainability, and performance of a service. You can use techniques such as service layering, service abstraction, or service categorization to classify services by granularity. For example, based on the potential services that you identified in the previous step, you might classify them into the following layers: business process services, business services, and application services.

4 Step 4: Classify services by type

The final step is to classify the potential services by their type, which refers to the nature and purpose of a service. Type can affect the design, implementation, and governance of a service. You can use techniques such as service modeling, service specification, or service contract to classify services by type. For example, based on the potential services that you identified in the previous step, you might classify them into the following types: task services, entity services, and utility services.

By following these four steps, you can identify and classify services into different types and levels of granularity in SOA. This can help you design and implement services that are aligned with your business domain, reusable across different scenarios, and easy to manage and evolve.