13.5 Componentization Trail Maps

Each unique set of answers to the three architectural transformation strategy questions forms a trail map. A trail map describes a time-phased approach, consisting of up to three phases. Table 13-4 shows several sample trail maps. The first trail map shows componentization by user transactions (A1) in the first phase, followed by the data migration in the second phase (B3). All increments are deployed in parallel with the operational system (C1). The second trail map is a big-bang approach whereby everything gets developed and deployed in one phase. Twelve trail maps are possible given the three independent variables .

Table 13-4. Sample Trail Maps

Trail Map	Phase 1	Phase 2
A1-B3-C1	Componentization by user transactions (A1) Parallel operations (C1)	Data migration (B3) Parallel operations (C1)
A2-B2-C2	Componentization by related functionality (A2) Data migration (B2) Operational (C2)
A2-B3-C2	Componentization by related functionality (A2) Operational (C2)	Data migration (B2) Operational (C2)

Each trail map can be evaluated by cost, schedule, risk, and complexity. In any modernization effort, however, different stakeholders will have different opinions on the best way to proceed. It is important to develop consensus before moving forward.

To obtain that consensus in our case study, we held a componentization workshop to discuss the risks and benefits of each approach. After considering the ramifications of each trail map, the stakeholders agreed on the A2-B3-C2 trail map, in which the modernized components are developed based on related functionality, followed by the data migration. Parallel operations will not be used.

Once the architectural transformation strategy has been selected, it must be further developed. The code migration strategy must be refined by identifying the program elements to migrate in each increment, determining the number and types of adapters that must be developed, and revising the cost estimation accordingly . The data migration strategy must be refined by determining the number and type of data adapters, if necessary, and data migration procedures. This process is described in Chapter 15.

The fact that the RSS team selected this trail map does not mean that it is the only appropriate architectural transformation strategy. Each trail map, like each modernization effort, has its own unique characteristics.