Why Service Orientation Is Important to Each of the Cloud Models

When you have some of the background on what it means to take a service-oriented approach to architecting technology systems, you can begin to see the relationship between this approach and cloud computing. Services are important for cloud computing from both an infrastructure and an application perspective.

Service orientation permeates the cloud, and the cloud serves as an environment that can host other services (either at a technical or a business level). Therefore, cloud vendors need to think about the architecture of their platforms so they can support different business models. Here are two different scenarios that a cloud provider may have to deal with:

On the one hand, cloud providers built the cloud infrastructure on well-designed services with clearly defined black-box interfaces. These black-box services allow the cloud to scale. In order to execute this approach, the cloud infrastructure needs to be service-oriented.

On the other hand, companies building applications designed for the cloud tend to build them out as services, which makes it easier for customers and partners to use them. For example, SaaS providers need an ecosystem of partners that provides either complementary components or full applications that are important to sustaining and growing their businesses. Following a service-oriented approach is a prerequisite for partners desiring to build economically on these platforms.

In Part II of this book, we delve into each of the different cloud models — Infrastructure as a Service (IaaS), Platform as a Service (PaaS), Software as a Service (SaaS), and Business Process as a Service (BPaaS). We illustrate how each of these models exhibits some important characteristics, such as elasticity and self-service provisioning.

This section shows how a services approach is critical to the development of each of these cloud models. Check out Part II for more information on the various ways that cloud services are created and deployed.

Infrastructure as a Service

The IaaS layer offers storage and compute resources that developers and IT organizations can use to deliver custom business solutions. A cloud provider wants the provisioning capability associated with the IaaS to be designed as a modular service with published interfaces so it can be used for many different situations.

Say that you have a group of applications that you want to run in a public cloud because you want capacity on demand. You sign up with an IaaS provider. Via your web browser, you can buy this capacity and start running your applications on the service. The service is provisioning the capacity. While you’re running the application, the service provisions hardware to run it and then de-provisions the virtualized servers when you’re done.

As a user of this capacity provisioning service, you don’t need to know how the provider is making the service happen; it’s a black box to you. If the cloud weren’t service oriented, you’d have to figure out how to provision your application to the environment. With the cloud, you can use a single provisioning service.

Platform as a Service

The PaaS layer offers development environments for IT organizations to use to create cloud-ready business applications. This model is offered as a set of black-box services that enables developers to build applications on top of the compute infrastructure. This might include developer tools that are offered as a service to build services, or even data access and database services, or even billing services.

In these situations, the principles of service orientation (such as loose coupling and reusability) are applied to IT infrastructure components that are delivered as cloud services to PaaS users. Developers in your organization may locate the platform services they need by referring to a service catalog.

Software as a Service

With SaaS, the provider hosts the software for you so that you don’t need to install it, manage it, or buy hardware for it. All you have to do is connect to it and use it.

For example, you might make use of CRM as a service or accounting as a service. Many of these providers have created their services in a modular way to enable scalability (because you’re using these services along with perhaps thousands of other clients). A services-oriented approach allows the provider, for example, to swap out functionality easily.

In all these models, companies will use a set of well-defined services that they can access through interfaces. Companies can leverage these services in many different ways, depending on the problems they’re trying to resolve.

Companies benefit from service orientation and the cloud because both of these approaches place a priority on understanding what the business needs, when it needs it, and how efficiently and cost-effectively the business can be served.

Business Process as a Service

With BPaaS, the service provider creates a set of commonly used processes that can be connected to other environments including IaaS and SaaS. A service provider or a developer could use a BPaaS to design a business process.

An example of a business process might be a way for a retailer to including a shipping service as part of the e-commerce system. Because these services are written as an independent service, it makes it easier to add new business processes to either serve a different constituent or automate a new business initiate.