The purpose of the Interface catalog is to scope and document the interfaces between applications to enable the overall dependencies between applications to be scoped as early as possible.

Systems will create, read, update, and delete data within other systems; this will be achieved by some kind of interface, whether via a batch file that is loaded periodically, a direct connection to another system's database, or via some form of API or web service.

The mapping of the Application Component-Application Component entity relationship is an important step as it enables the following to take place:

• Understand the degree of interaction between applications, identifying those that are central in terms of their dependencies on other systems
• Understand the number and types of interfaces between applications
• Understand the degree of duplication of interfaces between applications
• Identify the potential for simplification of interfaces when considering the target Application Portfolio
• Support the gap analysis and determine whether any of the applications are missing and as a result need to be created

The Interface catalog contains the following metamodel entities:

• Logical Application Component
• Physical Application Component
• Application communicates with application relationship