It is easy to experience pitfalls while expanding IT Architecture to consume cloud services. While larger companies can afford to hire consulting services and external integrators, it is good to have an understanding of the basics to set expectation with vendors or even within the company. This can help plan speed of the cloudintegration or choosing which services to consume. The underlying assumption in this article; the organization has evolved from legacy tightly coupled systems to SOA design across the enterprise (including shared services)
The simplistic representation of the workflow has a 3 tier architecture (database tier, business tier, client tier). Some clients prefer the data tier, logic tier and presentation tier representation. The data tier is where the enterprise data is stored. It can be stored in a database or file system. The data may reside in multiple systems (DBs). The data is retrieved from the data tier by the logic (business tier), processed and then finally passed onto the user. The logic tier processes user commands, applies core business logic, performs data validation and data aggregation. The logic tier acts as the glue between the data tier and the presentation tier. The presentation tier translates the business data into a format user can view or understand or translate user intent into a command the logic tier can process.
Workflow can be integrated with the cloud at any level within the 3 tier design or the complete service ( horizontal service or vertical service) may be replaced . The same arguement holds good for a n-tier system. A good system design (de-coupled) should permit replacement of either horizontal or vertical service with a cloud service. It is important to note - a cloud service does not change the service we consume ("what"), it changes the "how" we consume the service. Horizontal services include services such as payroll, HR, benefits, procurement etc. Vertical services include services such as healthcare (digital care management - transfer patient information across clinics), insurance (policyholder information across systems) etc. Firms benefit from best in class services, metered services, higher granularity of services when they migrate to the cloud. Firms can choose to integrate with IAAS (infrastructure as a service), PAAS (platform as a service) or SAAS (Software as a service) providers. Some firms are integrating with IAAS providers based on their business model (example integrating with Amazon web services - permits you to scale servers, DB's automatically based on season demand) to focus on core business.
Overall, firms need to decide on their roadmap for integration with cloud services. By 2015, most companies will be operating in a mix of on-premise, private cloud, public cloud, hybrid (virtual private) cloud environments. It is best to start thinking of the future now.