What is the main function of the exposure property in a dbt project?

The exposure property in a dbt project is primarily utilized to connect the project to external applications, which is why it serves as the correct answer. By defining exposures, analysts can document how data models are being utilized by various stakeholders, promoting a clear understanding of the relationships between data assets and their use cases. This facilitates better communication within teams and improves the awareness of data-driven decision-making processes.

In contrast, the other options do not accurately reflect the primary purpose of the exposure property. Logging the usage of data is more aligned with understanding how often models are accessed, which is not the main goal of exposures. Highlighting data transformation steps is generally handled through other aspects of a dbt project, such as documentation and model descriptions. Defining sources is a distinct function in dbt, primarily focused on establishing the origins of the data being transformed rather than illustrating how those transformations are exposed to users or applications.