The building block of Upala is a group. Groups consist of users. These can be anyone, friends, work communities, even entire identity systems. A user can become a member of multiple groups.
Groups assign scores to its members. Scores are valued in dollars. The way scores are assigned is arbitrary. Groups may require to pass a human verification test, prove activity in a social network, deposit money, etc. Scores could be individual or equal for all users.
Scores are valued in dollars
Every group is required to maintain a pool of money. Any member can steal from it the amount of money that equals their score. In exchange their ID is destroyed forever. The procedure is called liquidation (or explosion). The possibility of an explosion is what incentives groups to let only trusted members in and assign scores carefully.
Score is the reward for self-liquidation
A DApp (or any smart contract) decides which groups to trust. Users from those groups can prove their scores to the DApp. To prove the score the corresponding amount must be available in the group pool for liquidation. Groups may require fees for providing scores.
DApps nominate groups as their score providers and pay fees.
Wrapping it up the protocol allows to see how much a group “staked” on each user - “who (group management) allowed to hold how much money (score) to whom (user)”. Which reflects the user reputation in the context of the group.
Groups may significantly vary in their entry tests, scoring parameters, pool sizes, fees, governance models, etc. The way multiple groups are combined is also arbitrary. Depending on how groups are designed and combined different use cases are possible (see Use-cases).
As we have just seen Upala score represents user reputation relative to a group measured in dollars. It can be used “as is” to establish trust between group members. However the specific role for the score which we expect to become a widespread standard accepted by many DApps is Price of forgery.
If a group requires a user to pass a human verification (HV) test to become a member, the score may be set to represent the forging price for that HV test.