Multiverse - dApp Rollback Handler

A blockchain in itself is the persistent storage of the state of the ledger. Each block of the blockchain contains the logs of the operations applied to the ledger at a given point in time. If you attempt to take a look at the blockchain in its entirety, you would only see a consistent immutable line that expands infinitely forward. This is the case because the blockchain is designed to be an indefinitely growing succession of blocks. As I write this document there are about 700 thousands blocks in Bitcoin's blockchain and about 6 millions blocks in Cardano's.

However, as you start zooming toward the head of the blockchain you will begin seeing the blockchain grow. This is where history is being written, where the exciting part is happening. Most of us as users of blockchains will be most interested in what is happening here, wherein new changes to the distributed ledger are being applied. Depending on the way the active participants are cooperating to maintain the distributed ledger (depending on the consensus algorithm) the head of the blockchain may look more or less broad, more or less messy. Branches may appear, sometimes short lived ones, and sometimes seemingly at random. Every blockchain protocol aims to have them be short lived, but sometimes they may persist for longer than preferred or expected. We have already seen explicit forks happen on other blockchains which have taken on a life of their own and built out their own ecosystem. These are competitive snapshots of the ledger and hopefully the blockchain protocol will help resolve these fairly quickly.

From a user perspective, these competitive variants of the timeline are not necessarily relevant. Often these snapshots will intersect in the changes they are applying to the ledger, with some transactions potentially even appearing in both variations (though this is not always the case). With these competing variants continuing forward, eventually the blockchain may operate what is referred to as a rollback. In essence a rollback is the blockchain simply "changing its mind" (based on predefined rules) about which variant is the preferred one.

 The Multiverse is an innovative approach to reading and representing the state of blockchains. It provides nodes a competitive edge by maintaining and eventually participating in the various branches of a chain. This has waterfall effects through the entire stack, wherein various pieces of core ecosystem tooling such as blockchain explorers will be able to benefit significantly as well. Lastly, this also translates to a better end user experience, which we will cover in addressing how user wallets can maintain state via the Multiverse data structure directly.

A deep dive into the design of the Multiverse can be found here: https://docs.google.com/document/d/1sdtKb-wjNWV2sdJzNRxcfQpWcrV1MbMeBS819Udv9Dk/edit