There are several dimensions to defining an architecture. 
Consider:

• Defining which organizational changes are planned
• Defining the consequent architecture requirements
• Defining the characteristics of that architecture   

To ensure that all these dimensions receive sufficient attention, we never develop an architecture without an implementation plan. We do this before the architects focus on detail. This ensures that, prior to implementation, issues such as architectural objectives; nature and use are well thought out. This also guarantees that we have essence to fall back on during the definition of the architecture.

In addition to standard components such as milestones; resource planning; project organization etc., architecture specific components need to be included in the implementation plan, such as: objectives; audience; perspective; use and acceptance.

Many of the architects focus on detail. That is fine; however, the detail should serve a clear purpose which requires buy-in and acceptance. That is why it is paramount that appropriate attention be afforded to filling in the previously identified elements. Should this not happen, there is a very real danger that the architect will drown in detail, overshoot his objectives and deliver a product that has no buy-in.

A template for the Execution Plan is available here.