If there is a component in a system that publishes and accepts events, can you consider that as an example of an EDA pattern? The answer to the question is a clear no. In this section, we will examine the characteristics of EDA patterns. Their main characteristics are the following:

• Multicast communications: The publishers or the participating systems have the capability to send events to multiple systems that have subscribed to it. In other words, it is not a unicast communication in which one sender can send data only to one receiver.
• Real-time transmission: Publishers publish the events as and when they occur in real time to the subscribers. In other words, the mode of processing or transmission involved here is real time and not batch processing.
• Asynchronous communication: The publisher does not wait for the receiver to process an event before sending the next event.
• Fine-grained communication: Publishers keep publishing individual fine-grained events instead of waiting for a single aggregated event.
• Ontology: EDA systems always have a technique to classify events in terms of some form of a group/hierarchy based on their common characteristics. This gives flexibility to the subscribers to subscribe to a specific event or specific category of events.