Preface

You and I have never met. I have no idea what your business is. However, I do know what your enterprise architecture looks like. I can even show you the exact picture you use to describe your enterprise system. Take a look at Figure P.1. Look familiar?

Figure P.1. The Picture You Show of Your Enterprise System

It goes without saying that your enterprise is a perfect three-tier (or N-tier) software architecture. When describing your system, you wax poetic about your perky presentation tier, accepting HTTP requests from complacent clients and SOAP requests from congenial collaborators. You illuminate in minutiae how you manage your middle tier , running well-behaved business logic cherubs, all gleefully sharing database connections and other valuable system resources. Behind all of this, your enterprisewide database shouts encouragement from its sheltered back end.

See? I told you I know what your enterprise architecture looks like. I also know one other thing. I know you lie. You lie through your teeth. Your enterprise architecture looks nothing like Figure P.1. Do you want to see the real picture of your enterprise architecture? Take a look at Figure P.2. But first sit down. It isn't pretty!

Figure P.2. Your Real Enterprise Architecture

In the real world your clients are not meek, but malicious. Your middle tier is not well behaved, but made up of a disparate bunch of applications developed without regard for the needs of their stablemates. Your "database" is not an enterprisewide anything, but rather a series of disorganized data storage technologies that spend most of their time cringing from the unreasonable and often conflicting demands of the business logic.

As architects , we have two choices. We can ignore this chaos, or we can model it. When we model it, we have the opportunity to bring it under some degree of intellectual control.