By Serge Thorn, Architecting the Enterprise
This is the second installment of a three-part series discussing how to implement SOA through TOGAF®. In my first blog post I explained the concept of the Center of Excellence, and creating a vision for your organization.
The SOA Center of Excellence (CoE) will need to define a Reference Architecture for the organization.
A Reference Architecture for SOA is an abstract realization of an architectural model showing how an architectural solution can be built while omitting any reference to specific concrete technologies. Reference Architecture is like an abstract machine. It is built to realize some function and it, in turn, relies on a set of underlying components and capabilities that must be present for it to perform. The capabilities are normally captured into layers, which in their own right require an architectural definition. However, the specific choice of the components representing the capabilities is made after various business and feasibility analysis are performed. A Reference Architecture can be used to guide the realization of implementations where specific properties are desired of the concrete system.
The purpose of the Reference Architecture is reflected in the set of requirements that the Reference Architecture must satisfy. We can structure these requirements into a set of goals, a set of critical success factors associated with these goals and a set of requirements that are connected to the critical success factors that ensure their satisfaction.
A Reference Architecture for SOA describes how to build systems according to the principles of SOA. These principles direct IT professionals to design, implement, and deploy information systems from components (i.e. services) that implement discrete business functions. These services can be distributed across geographic and organizational boundaries, can be independently scaled and can be reconfigured into new business processes as needed. This flexibility provides a range of benefits for both IT and business organizations.
Using the pattern approach the SOA Reference Architecture is a means for generating other more specific reference architectures, or even concrete architectures depending on the nature of the patterns. Or to put it another way, it is a machine for generating other machines.
The Open Group SOA Reference Architecture (SOA RA) standard is a good way of considering how to build systems.
The SOA CoE needs also to define the SOA lifecycle management that consists of various activities such as governing, modelling, assembling, deploying and controlling/monitoring.
Simply put, without management and control, there is no SOA only an “experience”. The SOA infrastructure must be managed in accordance with the goals and policies of the organization, which include hardware and software IT resource utilization, performance standards as well as goals for service level objectives (SLOs) for the services provided to IT users as well as business goals and policies for businesses that run and use IT. To be truly agile, enactment of all these different types of policies requires automated control that allows goals to be met with only the prescribed level of human interaction.
For every layer of the SOA infrastructure a corresponding Manage and Control component needs to exist / be in place. Moreover, the “manage and control” components must be integrated in a way that they can provide an end-to-end view of the entire SOA infrastructure.
These manage and control functions provide the run-time management and control of the entire enterprise IT execution environment. This includes all of the enterprise’s business processes and information services, including those associated with the IT organization’s own business processes.
The “Principle of Service orientation” must exist as defined in the TOGAF® 9.1 Framework in section 22.7.1.1 Principle of Service-Orientation, but lower levels of principles, rules, and guidelines are required.
Needs and capabilities are not mechanisms in the SOA Reference Architecture. They are the guiding principles for building and using a particular SOA. Nonetheless, the usefulness of a particular SOA depends on how well the needs and capabilities are defined, understood, and satisfied.
Architecture principles define the underlying general rules and guidelines for the use and deployment of all IT resources and assets across the enterprise. They reflect a level of consensus among the various elements of the enterprise, and form the basis for making future IT decisions.
Guiding principles define the ground rules for development, maintenance, and usage of the SOA. Specific principles for architecture design or service definition are derived from these guiding principles, focusing on specific themes. These principles are the characteristics that provide the intrinsic behaviour for the style of design.
In the third and final installment of this series I will discuss how to relate SOA principles back to business objectives and key architecture drivers.
Serge Thorn is CIO of Architecting the Enterprise. He has worked in the IT Industry for over 25 years, in a variety of roles, which include; Development and Systems Design, Project Management, Business Analysis, IT Operations, IT Management, IT Strategy, Research and Innovation, IT Governance, Architecture and Service Management (ITIL). He is the Chairman of the itSMF (IT Service Management forum) Swiss chapter and is based in Geneva, Switzerland.