[CS] Four properties for TRB and Consensus

TRB(Terminated Reliable Broadcast)는 하나의 값을 여러 곳으로 보내 동일하게 저장해 두기 위한 방법이라고 볼 수 있다. 한편, consensus는 여럿이 값을 제안하고 일치 과정을 통해 동일한 값을 가지도록 하는 방법이다. 시험을 보기 위해 외워야 해서 네가지 property를 써본다. 

TRB (Terminated Reliable Broadcast) 

Validity: If the sender is correct and it broadcasts a message m, then all correct processes eventually deliver m. 

Agreement: If a correct process delivers a message m, then all correct processes eventually deliver m. 

Integrity: Every correct process delivers at most one message, and if it delivers m(!=SF), then some process must have broadcast m. 

Termination: Every correct process eventually delivers some message. 

Consensus

Validity: If all processes that propose a value propose v, then all correct processes eventually decide v.

Agreement: If a correct process decides v, then all correct processes eventually decide v.

Integrity: Every correct process decides at most one value, and if it decides v, then some process must have proposed v.

Termination: Every correct process eventually decides some value.