Balancing Enterprise Context and Detail with Services
In modern enterprise architectures, the ideal balance between strategic context at the enterprise level and the lower-level of detail that is required to assemble infrastructure, manage information, and build applications, pivots on the logical concept of business services. Business services make up the linkage point between the constructs of business vision, strategy, and their requisite business capabilities with the implementation of those constructs as realized in applications, information models, processes, and applications.

EA Drives Services Orientation
Service orientation is one of many ways to conceptualize and deliver holistic enterprise architecture. It is not, in itself, the enterprise architecture, though it is hard to dispute that the concept of service orientation seems a natural fit for business, SOA is no more the enterprise architecture of corporations today than EAI was a few years ago. As IT trends evolve in the future, it is likely that SOA will not be the chosen approach. One of the only things we can really count on is that things will change. EA is much more than its resultant design and directional choices. It is the process that leads to design and directional decisions. The EA process embraces change by its very nature. EA teams of the future will continue to combine analysis of environmental factors, business vision and strategy, information technology trends and directions, investment priorities, and best-practices of the day in order to create the enterprise architecture directions relevant at that time.

Today, SOA and service orientation in general seem a logical choice for many enterprises. It is also worth noting that it may not be the choice for everyone. Whatever the degree/scope/size/rate of the SOA strategy, the way those services are implemented, how they grow and evolve, and even how they will eventually be replaced, are simply business as usual for the process of enterprise architecture.

Figure 2 diagrams the many aspects of the EA process that make it the ideal center of gravity for driving an SOA strategy.

Note the many feedback loops built into the process. A well-constructed EA process is dynamic and flexible to ongoing change. It is driven by executive management either through global business strategy changes or for the immediate needs of shorter-term tactical goals, objectives and targets. The numbered steps in Figure 2 illustrate the process:
1) Executive management - through declarations of large scale business vision and the portfolio of strategic intent - communicate the global business strategy to the enterprise.
2) The EA function interprets and analyzes the implications of that strategy, creating an integrated top-level model for the future state architecture that can deliver the required business capabilities in the way needed to optimize the operating parameters desired by management. These models reflect the intersection of business services, business functions, processes, information, technology, applications, and ultimately the required services. The resulting catalog of services and the portfolio of required enabling capabilities provide a powerful snapshot to guide current and future design decisions.
3) Comparing the currently installed elements of the enterprise to the future state model creates a clear picture of gaps in infrastructure, application, information and business services, suggesting possible projects meant to close those gaps and fulfill the vision.
4) The future-state EA provides directives in the form of policies, principles, technologies, techniques, and other models to guide proper development and synchronization of services. Some of these models include common information and data models, metadata definitions, common-use cases for business processes, etc., so that services created independently will work together by design.
5) As new tactical project suggestions arise from operational or other tactical requirements, they can be reconciled against the aggregate project portfolio created from the future-state EA. This provides the opportunity to respond in a way that will not jeopardize the enterprise strategic objectives.
6) The EA process is governed by an authoritative collection of approval, compliance, variance, escalation, and portfolio processes ensuring that the right services are implemented in the proper way, in the correct order, and with all dependencies properly accounted for.

The Potential of SOA - Delivered through EA
Imagine an enterprise constructed from business services aligned exactly to the required business capabilities. There are neither too many nor too few of these services; they mutually support one another, are flexible and adaptive; and they connect via well-defined, clean interfaces that are contextually consistent. These services hide unnecessary details, are simple to maintain and can optionally be sourced from multiple places. Silos don't exist, and the organization no longer wastes time, resources, or money on duplicate, overlapping, and ill conceived SOA projects. This is the reality of an EA-driven services oriented approach. EA provides the structure for top-down services orientation. Not there yet? An EA-driven approach models how the desired structure can be reached from the current-state architecture in the most direct, least painful way possible.