In previous chapters, I emphasized the need to transform enterprise architecture from a collection of static documents and diagrams into an operational tool that senior leadership can use to steer the enterprise toward achieving its goals. Until this point, we have discussed the need to clearly define the enterprise architecture and document it using formal models, but that does not automatically make your architecture a usable management tool. To make the architecture a real tool, you must be able to measure its effects on the enterprise. If you cannot measure the effects, you have no way of knowing if any of your actions have had any impact on the enterprise. The key to measuring those effects is monitoring your enterprise and comparing it to your architecture.