> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cow.bleu.builders/llms.txt
> Use this file to discover all available pages before exploring further.

# Arbitrating auctions

> This section gives a high level overview of the different components that are involved for CoW protocol batch auctions to take place.

## Architecture

```mermaid theme={null}
graph LR
    U[User] -->|Sign intent| OB[Orderbook]
    OB -->|Share orders| AP[Autopilot]
    AP -->|Send auction| D[Driver]
    D -->|Augmented auction| SE[Solver Engine]
    SE -->|Raw solutions| D
    D -->|Score| AP
    AP -->|Winner| D
    D -->|Settlement tx| BC[Blockchain]
```

Three main sub-systems are required to facilitate and drive the auction

### Order book

The [orderbook](/cow-protocol/explanation/architecture/orderbook) is the main entry point of the protocol for traders. Using the orderbook's API, UIs and other integrations allow traders to:

* Get quotes for orders
* Place orders
* Cancel orders
* Get the currently solved auction
* Etc.

For instance, when you visit [CoW Swap](https://swap.cow.fi) and place an order, the site uses the Order book API to add the order to a database. This database with all orders is shared with the **autopilot**.

### Autopilot

The [autopilot](/cow-protocol/explanation/architecture/autopilot) is a service that drives the core protocol functionalities with responsibilities including:

* Creating and arbitrating auctions
* Defining the timeline and valid orders for each auction
* Orchestrating the revelation and settlement of the winning solver's solution
* Monitoring the competition
* Serving as data consensus layer in the case of dispute or slashing by the DAO
* Communicating auctions to all registered solvers

### Solvers

For the sake of this documentation, we differentiate solvers into two sub-parts:

#### Driver

The [Driver](/cow-protocol/explanation/architecture/driver) is the executive part of the solving process, and is responsible for:

* Interacting with the blockchain in order to enrich, encode and eventually execute the settlement
* Preparing all the data needed for the engine to match orders in the auction and forwarding the augmented auction to the engine
* Receiving raw solutions from the solver engine, which it post-processes, simulates, merges, encodes into a blockchain transaction and finally scores

The driver interfaces with the autopilot and reports the best solution's score to participate in the competition. If chosen as a winner of the auction, the driver is also responsible for getting the solution included in the blockchain.

#### Solver Engine

[Solver Engines](/cow-protocol/explanation/architecture/solver-engine) implement the pure matching logic, by employing different types of solving algorithms to optimally match traders with one another taking on-chain as well as private liquidity into account. They receive the pre-processed auction instance from the driver sub-component and return the solution together with instructions on how to achieve the fulfillment on-chain.