In the Ethereum yellow paper Page 5 says that the log entry O consists of (O_a,(O_{t0}, O_{t1},...),O_d). And O_a means the logger's address. What's the meaning of logger's address? Does it mean the contract address or something can be defined by the user (like the SHA3 of (O_{t0}, O_{t1},...),O_d)? Thank you!
According to the yellow paper, the logger's address is a 20-bit number, i.e. the format of an Ethereum address. In Ethereum we can distinguish between externally owned account or contract account. The former cannot produce logs, therefore the logger's address is the contract, whose execution has generated the log (with the LOG1..LOG4 bytecode or with the solidity emit Event utility).
