# Overview

This section explains the fundamental building blocks of the Hermodr framework.

## Overview

```
┌──────────────────────────────────────────────────────┐
│                   Your application                   │
│                                                      │
│   ┌──────────────┐      ┌──────────────────────────┐ │
│   │  Event data  │─────▶│      EventPublisher      │ │
│   │  (annotated  │      └──────────┬───────────────┘ │
│   │   classes)   │                 │ fan-out         │
│   └──────────────┘        ┌────────┴────────┐        │
│                           │                 │        │
│                   ┌───────▼─────┐   ┌───────▼──────┐ │
│                   │  Channel A  │   │  Channel B   │ │
│                   │ (Azure SB)  │   │  (Webhook)   │ │
│                   └─────────────┘   └──────────────┘ │
└──────────────────────────────────────────────────────┘
```

1. You describe an event using an annotated data class (or construct a raw `CloudEvent`).
2. You call `EventPublisher.PublishAsync` (or `PublishEventAsync`).
3. The publisher fans the event out to **every registered `IEventPublishChannel`**.
4. Each channel serialises the event and dispatches it to the appropriate transport.

## Key Abstractions

| Abstraction                 | Role                                                                                                     |
| --------------------------- | -------------------------------------------------------------------------------------------------------- |
| `EventPublisher`            | The single entry point for publishing events                                                             |
| `IEventMiddleware`          | A composable step in the publish pipeline (enrichment, validation, observability, …)                     |
| `EventContext`              | Carries the current event, scoped services, options, and a data-sharing `Items` bag through the pipeline |
| `IEventPublishChannel`      | One transport target (Azure Service Bus queue, RabbitMQ exchange, …)                                     |
| `IBatchEventPublishChannel` | A channel that also supports delivering multiple events in a single batched call                         |
| `IEventFactory`             | Converts an annotated data object into a `CloudEvent`                                                    |
| `IEventIdGenerator`         | Generates unique identifiers for events (default: GUID)                                                  |
| `IEventSystemTime`          | Supplies the event timestamp (replaceable for testing)                                                   |
| Keyed `IEventPublisher`     | Resolves a named publisher pipeline by name at runtime                                                   |

## Pages in this section

* [CloudEvents Standard](/core-concepts/cloudevents.md)
* [Event Publisher](/core-concepts/event-publisher.md)
* [Event Creation](/core-concepts/event-creation.md)
* [Publish Pipeline & Middleware](/core-concepts/publish-pipeline.md)
* [Publish Channels](/core-concepts/publish-channels.md)
* [Event Annotations](/core-concepts/event-annotations.md)


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