What is the difference between evidentiary and dispositive documents?

In the field of diplomatics, documents are classified based on their legal function into two primary categories: evidentiary and dispositive.1

• Evidentiary documents: These serve merely to record a legal act that has already been executed orally. They act as proof or testimony that a transaction took place, but the document itself is not the source of the legal validity.1
• Dispositive documents: The act of issuing these documents constitutes the legal act itself. In this case, the document is not just a record of a past event but is the instrument that creates, modifies, or terminates a legal right or obligation.1

This distinction, which emerged among Roman documents starting in the 3rd century CE, highlights the evolution of how legal authority was formalized in historical records.1