Describe purpose of Poseidon

README.md

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+Poseidon provides containerized execution of arbitrary user code inside a Docker container for learning purposes. It has two main purposes:
+
+1. Securing the executions so that they are isolated from each other and from the host system.
+2. Being scalable enough to provide hundreds of executions per minute.
+   
+Poseidon also offers a live I/O connection to the running program via WebSocket.
+
+![Poseidon as mediator between CodeOcean and Nomad.](docs/resources/OverviewCodeOceanPoseidonNomad.png)
+
+Poseidon is designed to be used with [CodeOcean](https://github.com/openHPI/codeocean), a code-execution provider and auto-grader used in MOOC platforms.
+
+Poseidon requires a [Nomad](https://www.nomadproject.io/) cluster for scheduling its executions, which needs to be set up separately.
+
 ### Documentation
 
 For the OpenAPI 3.0 definition of the API Poseidon provides, see the [swagger.yaml](api/swagger.yaml).
 
 For the rest of the documentation see the [docs folder](docs). It describes...
 
-- some aspects of the [development workflow](docs/workflow.md) including setup guide. You should read this first when starting out with the project.
+- some aspects of the [development workflow](docs/development.md) including setup guide. You should read this first when starting out with the project.
 - [configuration](docs/configuration.md) of the system.
 - [security configurations](docs/security.md) (how to active access control and TLS with Poseidon).
 - [how Poseidon integrates Nomad](docs/nomad_usage.md) in its architecture.