Term
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Definition
Service Oriented Architecture is an architecture for building business applications using loosely coupled services which act as black boxes and can be orchestrated to achieve a specific functionality by linking them together.
- SOA components are loosely coupled
- SOA services are black boxes
- SOA services should be self defined
- SOA services are maintained in a listing
- SOA components can be orchestrated and linked to achieve a particular functionality
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Term
| In SOA, do we need to build systems from scratch? |
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Definition
| No, if you need to integrate or make an existing system as a business service, you just need to create loosely coupled wrappers which will expose the systems functionality in a generic fashion. |
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Term
| Explain business layers and plumbing. |
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Definition
| Business layer is the layer that contains business functions. Plumbing is the layer that contains technical details such as managing connections to DB, web server, etc. |
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Term
| What is the difference between a service and a component? |
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Definition
| A service is a logical grouping of components. A component is the implementation of part of a service. The components can be in any language, but a service will be exposed in a general format like Web Services. |
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Term
| Can you describe the complete architecture of SOA? |
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Definition
- ESB - guarantees delivery of messages between systems in a loosely coupled manner.
- SOA registry - describes what each service does, where they are located, how they communicate
- SOA workflow - defines workflows (how services interact, what order they execute) using the services in the SOA registry
- Service broker - read the workflow and ties the services together. This is normally middleware like Enterprise Application Integration (EAI) products.
- Process manager - The collection of the SOA registry, SOA workflow, and service broker.
- SOA supervisor - the "traffic cop" that ensures services do not have issues. Is mainly concerned with performance issues and sending messages to the appropriate architecture to fix any issues.
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Term
| What are ends, contract, address, and bindings? |
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Definition
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Term
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Definition
No. SOA is an architectural concept, and web-services are a technical approach to complete it. They are the preferred standard to achieve SOA.
Using SOAP as an example
- SOAP is loosely coupled as messages are sent using SOAP, which is XML based.
- The WSDL of a service describes the service
- The webservice can be located in a UDDI repository
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Term
| What is a reusable service? |
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Definition
Autonomous, reusable, discoverable, stateless functionality that can be part of a composite application or service.
Identified with a business activity described by service specs (design-time contract).
Constraints including security, QoS, SLA (Service Level Agreement), usage policies, may be defined by multiple run-time contracts, multiple interfaces, and multiple implementations.
Governed at the enterprise level throughout its entire lifecycle. Its reuse should be promoted through a prescriptive process and that reuse should be measured. |
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Term
| With service identification, which approach encourages reuse and maintenance, top-down or bottom-up? |
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Definition
| Top-down approach is business-driven, and can separate the concerns of business and IT. It is the most appropriate to improve reuse and ROI in the medium/long term. |
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Term
| How can loose coupling be achieved in SOA? |
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Definition
| One strategy is to use the service interface (WSDL for SOAP) to limit dependency of clients on the implementation. |
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Term
| Should the service of SOA be stateful or stateless? |
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Definition
Stateless. It may have a context within its execution, but it will not have an intermediary state waiting for an event. The retention of state-related data must not extend beyond a request/response on a service.
State management consumes a lot of resources, which can reduce the scalability and availability. |
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Term
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Definition
| The Enterprise Service Bus provides an infrastructure to implement the loosely coupled concept of SOA. ESBs also provide mechanisms for security, implementing some level of Service Level Agreements, routing and transformation capabilities, all of which vary to some extent from service to service. |
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Term
| What are the common pitfalls of SOA? |
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Definition
Viewing SOA as an end, rather than a means to an end. The end goal is to solve a specific business problem.
Another common pitfall is to try to solve multiple problems at once. This approach, starting with major organization-wide infrastructure investments, often fails to show results in a timely manner or to offer a compelling ROI. |
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