The physical model defines where the physical resources of the application are deployed to support the requirements of the other enterprise sub-models, and the process through which the competing interests of the sub-models are resolved. The completed physical model of an enterprise application is the application’s architecture. Some of the questions this model answers include:
As the diagram in the Enterprise Application Model shows, the physical model directly interacts with the user model, the logical model, and the technology model. The following table characterizes these interactions and gives brief examples of each.
Sub-model | How the physical model relates to it | Example |
User model | Provides the means by which the application is made available to the user. | The physical architecture must be able to support the user’s desktop configuration and scale efficiently to the number of users and their processing requirements. |
Logical model | Constrains the extent to which logical constructs can be mapped to the physical infrastructure. | An application that provides online transaction processing must define components that can interface with a transaction management infrastructure. |
Technology model | Limits the technology that can be supported on the physical infrastructure. | An application deployed to the public on the Internet must use "least common denominator" technology for user interface elements that must run on a variety of platforms and browsers. |
Since the development model permeates all of the Enterprise sub-models, there are no "typical" interactions because you must account for every design and implementation decision in the development model.
Examples of the way the Internet has impacted the physical model include:
For more information The physical model is explored in greater depth in "Designing the Physical Architecture," in Chapter 3, “Creating the Application Architecture.”