What are Important Function modules regarding workflow?

SWW_WI_DISABLE: For locking of work items against execution.

SWW_WI_ENABLE: For unlocking of work items for execution.

SWW_WI_CONTAINER_READ: To read the container elements of a particular work item

SWW_WI_DEADLINES_CHANGE: To change the attributes of the deadline monitoring for a particular work item