Common use of Problem Definition Clause in Contracts

Problem Definition. ‌ To agree on a given piece of information is a classical co- ordination problem in distributed computing. The Two Gen- erals’ Agreement Problem, formulated for the first time by ▇▇▇ ▇▇▇▇ [3] to illustrate the two-phase commit protocol in distributed database systems, is often used to explain the de- sign challenges when attempting to coordinate an action by communicating over a faulty channel, and can be described as follows. Two battalions are encamped near a city, ready to launch the final attack. Because of the redoubtable fortifications, the attack must be carried out by both battallions at the same time in order to succeed. ▇▇▇▇▇, the generals of the two armies need to agree on the time of the attack, and their Figure 1: N-way handshake between nodes S and R. only way to communicate is to send messengers through the valley. The latter is occupied by the city’s defenders, and a messenger can be captured and its message lost, i.e., the communication channel is unreliable. Since each general must be aware that the other general has agreed on the attack plan, messengers are used also to exchange acknowledg- ments. However, because the acknowledgement of a mes- sage receipt can be lost as easily as the original message, a potentially infinite series of messages is required to reach an agreement. A different problem that we are not addressing in this work is how to guarantee the identity of the sender of the message, as well as how to cope with misbehaving parties.

Problem Definition. ‌ To agree on a given piece of information is a classical co- ordination problem in distributed computing. The Two Gen- erals’ Agreement Problem, formulated for the first time by ▇▇▇ ▇▇▇▇ [3] to illustrate the two-phase commit protocol in distributed database systems, is often used to explain the de- sign challenges when attempting to coordinate an action by communicating over a faulty channel, and can be described as follows. Two battalions are encamped near a city, ready to launch the final attack. Because of the redoubtable fortifications, the attack must be carried out by both battallions at the same time in order to succeed. ▇▇▇▇▇Hence, the generals of the two armies need to agree on the time of the attack, and their Figure 1: N-way handshake between nodes S and R. only way to communicate is to send messengers through the valley. The latter is occupied by the city’s defenders, and a messenger can be captured and its message lost, i.e., the communication channel is unreliable. Since each general must be aware that the other general has agreed on the attack plan, messengers are used also to exchange acknowledg- ments. However, because the acknowledgement of a mes- sage receipt can be lost as easily as the original message, a potentially infinite series of messages is required to reach an agreement. A different problem that we are not addressing in this work is how to guarantee the identity of the sender of the message, as well as how to cope with misbehaving parties.