What is the primary difference between validationExpression and requestValidationExpression properties?

The primary difference between the validationExpression and requestValidationExpression properties lies in when they are applied within the data validation process in Guidewire applications.

The validationExpression property is utilized to validate individual widgets or fields as the user interacts with them. This means that it triggers validation checks whenever there is an update to the widget, ensuring that the input meets specific criteria in real-time as the user inputs data. This immediate feedback mechanism enhances user experience by allowing users to correct errors promptly.

On the other hand, the requestValidationExpression property comes into play when the server processes a request. It validates the data only once the request is sent to the server, which typically occurs when the user submits a form or triggers an action that requires server communication. This step ensures that all the data collected from the user meets the necessary validation rules before it is processed or saved on the server.

Thus, the correct answer highlights the operational difference: validationExpression checks validation on widget updates in real-time, while requestValidationExpression validates data upon server requests. This distinction is critical for developers to understand how to implement effective validation strategies in their applications.