Timestamp Ordering Protocol
A timestamp is a tag that can be attached to any transaction or any data item, which indicates a specific time on which the transaction or data item had been activated in any way. We, who use computers, must all be familiar with the methods of "Date Created" or "Last Modified" properties of files and folders. Well, timestamps are things like that.
A timestamp can be executed in two ways. The simplest one is to directly assign the current value of the clock to the transaction or the data item. The other policy is to attach the value of a logical counter that keeps incrementing as new timestamps are needed.
The timestamp of a transaction shows the time when it was first activated. The timestamp of a data item can be of the following two types:
W-timestamp (Q): This means the latest time when the data item Q has been written into.
R-timestamp (Q): This means the latest time when the data item Q has been read from.