SOA Adoption Models
We have encountered various approaches that enterprises are taking for migrating to and adopting SOA for their enterprises. We list the following models in this article that we have come across consistently: ad hoc and program-based (organic and strategic) models.

The Ad Hoc SOA Adoption Model
Ad hoc SOA adoption is the project-level adoption of service-oriented technologies on a specific need or tactical basis. There is no central coordination or plan. The results of this adoption model are:
• Each project or initiative benefits the technical advantages of new services at an individual level.
• The technologies are applied inconsistently, which allows for proliferation of bad SOA practices, such as the development of non-standard Web Services, hidden pockets of cost in one-off maintenance, low-level of service reuse, increase in point-to-point Web Services connectivity, etc
• Enterprise reuse can't be achieved and can therefore yield redundant development efforts.
• Increased IT complexity, resulting in reduced agility for responding to business demands
• Potentially resulting in worse condition than the previous status quo.

It's clear that businesses need to invest in a strategy for SOA adoption that will address business drivers, improve existing IT challenges, and avoid the negative impact of unplanned ad hoc SOA adoption. Depending on the organization's goals and level of investment, SOA adoption can be planned in accordance with an overall program.

The Program-based SOA Adoption Model
Program-based SOA adoption allows SOA evolution to be controlled according to an overarching enterprise strategy and goals. This model provides a holistic view and addresses the enterprise from organizational, process, and technology dimensions over time. A planned and directed SOA adoption strategy eliminates the risk of propagating SOA bad practices that will worsen the IT situation. Some key characteristics of a program-based approach are:
• Creates processes and guidelines that support desirable, consistent, predictable, and measurable outcomes for SOA adoption.
• Provides active service portfolio management, including ongoing SOA opportunity identification.
• Promotes SOA best practices and enhances one's ability to adopt new technology paradigm consistently across the enterprise as well as increase SOA ROI
• Provides an opportunity for changes to the organization and processes as learning can be applied to further strengthen the SOA ROI.

We'll consider two program-based SOA adoption models: organic and strategic. Both provide planned and controlled adoption behaviors. The difference in these models is how they are initiated and the pace of adoption. (See Sidebar)

The Program-based Organic SOA Adoption Model
Organic SOA adoption model requires low investment. It allows:
• Quick understanding and alignment of key business drivers with SOA objectives
• Execution of a prioritized project using SOA principles
• Development of core (base line) processes
• Building foundation technologies that can be used for successive SOA projects.

In an organic adoption model of SOA, one builds a business case from the findings of the initial project. Base line standards, best practices, processes, and organization structure are created and then evolved. The initial project rarely provides a positive ROI due to the cost associated with additional planning and the SOA infrastructure build-out. However, the organic model shows that incremental benefits will be achieved through SOA on successive projects. SOA does not require a full enterprise implementation to begin to realize value. Investments in the infrastructure can be aligned on a project basis to reduce risk. The value can be realized earlier without a comprehensive SOA strategy.

Figure 1 shows the typical progression of the organic SOA adoption model. The initial project is chosen opportunistically from existing planned projects according to agreed upon criteria. The project is executed with the original scope in mind and a specific business problem is solved. SOA artifacts and processes used on the project are then harvested. Incremental SOA costs are absorbed by the initial project and are recouped by the business in subsequent SOA projects.

The Program-based Strategic SOA Adoption Model
As an alternative to the organic approach, the strategic SOA adoption model is characterized by an initial strategy project to build an enterprise business case for SOA, define a future state, and plan a roadmap for implementation. The future state incorporates not only the technology transformation required to move towards SOA, but also the organizational and process changes as well. (Figure 2)

Organizations adopting SOA through a strategic model build out a supporting infrastructure for enterprise SOA with a reference implementation that demonstrates the recommended use of standards and best practices.

The roadmap of strategic SOA is based on a comprehensive assessment of the enterprise and defines SOA projects over a three- to five-year timeframe. It takes into account all the dimensions of an enterprise: people, processes, and technology (see Figure 3). NOTE: We need to redraw this visual differently. It was done for PMUSA with ToPCoder).

SOA Adoption Recommendations
While there are clear tradeoffs between the organic and strategic SOA adoption models, there are four key adoption recommendations for any successful program-based SOA. They are:
• Align SOA objectives with business drivers
• Selectively determine SOA adopters
• Identify and address organizational barriers to adoption
• Define and measure success

Align SOA objectives with business drivers
Since SOA is a set of best practices and related standards that can be applied uniquely on each implementation, implementation can produce a variety of benefits. There's a risk of misfiring or misinterpretation when SOA objectives aren't clearly aligned with business drivers. To be effective, SOA implementation objectives have to be in alignment with the enterprise imperatives for both organic and strategic adoption. In both organic and strategic SOA adoption, SOA objectives need to be documented that can:
• Support the business case for SOA
• Align the architecture with the needs of the business
• Act as a reference for developing a future-state reference architecture
• Prioritize the approach for potential projects and a SOA roadmap

SOA strategy should begin by understanding the enterprise imperatives - a successful business plan takes the external environment, business and IT strategy, and current and planned projects into account. SOA objectives are best identified collaboratively in a workshop environment with key SOA stakeholders from business and IT leaders along with user communities. With enterprise imperatives identified, SOA objectives can be well articulated and prioritized across functional units of the value chain.

Earlier we showed you typical business drivers for SOA (Table 1). SOA objectives for the enterprise can be an extension of these kinds of drivers prioritized and aligned with the enterprise imperatives. For example, the first business driver - lower cost of IT - simplify the IT infrastructure - can be the basis of a SOA objective and can be extended to state - lower cost of IT - simplify the IT infrastructure by reducing the data redundancies across customer-oriented systems. An SOA objective should relate to a particular business strategy, but not prescribe an implementation approach.