Delegated Proof of Stake (DPoS) is a variant of Proof of Stake (PoS), a trade-off solution between the decentralization and the network response speed. The elected group of block producers (witnesses) and scheduling production are two important components in the DPoS system.
The witness election process is to make sure the stakeholders are in control. Therefore, the witnesses are voted in power based upon the total stakes the voters (users of the network) own. Each user can vote maximum 30 witnesses. Top 20 witnesses are granted for creating and signing new blocks. Witnesses Rank 21st are backup witnesses. The voting is not a one-time job. Voters can also vote to remove witnesses in next round if they misbehave, such as censor transactions, double spend and etc.
Another key element to enhance the security and integrity of blockchains is to create new blocks on schedule by the elected witnesses. After a block is created, it will be finalized (i.e. cannot be reversed) only when it receive votes from (2/3+1) of 20 witnesses. Otherwise, the longest chain rule is followed. Scheduled production rate is a block per 3 seconds. Therefor the blockchain response time is 40 seconds (3202/3 = 40).
For Hardforks and key protocol changes, the consensus rule is the approval by 17 out of 20 witnesses.
The content in Addressing 51% attacks should be more accurate and complete. Now it is very political. Feel, don't have any good solution. Delayed voting is not a solution but a patch. In my opinion, the issue in DPoS system is that the vote based upon stakes comes too easy, no any pain and cost. Introducing Proof of Burn philosophy into DPoS might be a not bad idea. However, till day Hive still purely reply on DPoS algorithm. I don't feel the confident that Hive will be protected from 51% attacks again in the future.
My bread and right record: Today I still have 0.065 HIVE, 100% Vote power, 0 Vote Value.