What does a custom data type (CDT) represent in Appian?

A custom data type (CDT) in Appian represents a logical grouping of related data. This concept allows developers to define structured data that can include multiple fields and data types, which are typically related to a specific entity or function within an application. By creating a CDT, users can encapsulate and organize data in a meaningful way, which enhances clarity, reusability, and maintainability within the application.

One of the key advantages of using CDTs is their ability to streamline data handling. For example, instead of managing individual data fields separately, a CDT allows for managing a complete record, making it easier to pass data between processes or interfaces. This structural organization contributes significantly to the application's overall efficiency.

Predefined data structures without modifications do not capture the flexibility and customization that CDTs offer. Similarly, user roles and external database connections refer to entirely different functionalities within Appian, focusing respectively on access control and data retrieval mechanisms. Therefore, it's the logical grouping aspect of CDTs that makes option B the correct choice.