Court assemblies at this time fell into three categories: regular assemblies, grand assemblies, and special assemblies.
Regular assemblies were the scheduled deliberations of officials in the Department of State Affairs. These were the routine procedure for handling major affairs of state, which was why the Department of State Affairs was called the hub of government, equivalent to a modern state council. A diligent Son of Heaven attended every session; a less diligent one attended some and skipped others. Attendance was called "presiding at court"; in his absence, the results of the deliberations were submitted to him in writing.
Grand assemblies meant ceremonial gatherings such as the New Year's Day assembly. These were occasions when the emperor and all his officials truly gathered in one hall, and attendance was mandatory for both. An official who failed to appear was charged with "defaulting on the rites of the court assembly" and faced impeachment.
Special assemblies were convened ad hoc, generally to address a particular matter, and came in two forms.
In one, the Son of Heaven summoned specific senior officials-imperial princes, dukes and marquises, officials of the Gate Department, Mounted Attendants, and those ranked at two thousand bushels or above-to deliberate. In such cases, the Son of Heaven attended, and officials could not absent themselves without cause.
The other was a broad deliberation of officials within and without, also called a "Court Deliberation" during the Han dynasty. The Son of Heaven might or might not attend, though more often he did not. Apart from the Eight Seats of the Department of State Affairs, who had to lead the deliberations, officials currently on duty, occupied with official business, or otherwise unable to attend were permitted to stay away.
Today's assembly of officials of the sixth rank and above belonged to this latter category