An abstraction of design activity on a signal interface into a class-based environment, to allow higher-order verification intent to be expressed more concisely. The unit of data that is passed along TLM connections in UVM. When the stimulus strategy involves UVM sequences, the transaction is also known as a Sequence Item.
A transaction is a collection of information that is passed from point A to point B, and may have a beginning time and an ending time. A transaction may have relationships with other transactions - like transaction X is the parent of transaction Y (and transaction Y is the child of transaction X).