Which two elements are optional in a SOAP fault message?

In a SOAP fault message, the optional elements are specifically designed to provide additional context in case of an error during the processing of a SOAP message. When considering the structure of a SOAP fault, it usually includes mandatory elements like FaultCode and FaultString, which are essential for identifying the nature of the fault and providing a human-readable explanation.

The elements FaultActor and details can be classified as optional. FaultActor specifies the specific node or actor that generated the fault, whereas details can include application-specific error information that provides further insight into the issue. This means that the presence of these components can vary depending on the specific SOAP implementation and is not strictly required for a SOAP fault message to be valid.

By understanding the structure of a SOAP fault message, it becomes clear that FaultCode and FaultString are fundamental to conveying necessary error information, while FaultActor and details enhance fault description but are not essential to the integrity of the SOAP fault format. This distinction clarifies why the identified answer is correct.