### Querying Events with DCB Tags (Pseudo-code)

Source: https://dcb.events/index

This pseudo-code demonstrates how to query events in a DCB-compliant Event Store by specifying event types and tags. It illustrates filtering events to check for course and student existence, and counting subscriptions, which can be combined for complex queries. This approach allows for selective retrieval of relevant events based on specific criteria.

```pseudo-code
[
  {
    "event_type": "course defined",
    "tag": "course:c1"
  },
  {
    "event_type": "student registered",
    "tag": "student:s1"
  },
  {
    "event_type": "student subscribed to course",
    "tag": "course:c1"
  },
  {
    "event_type": "student subscribed to course",
    "tag": "student:s1"
  }
]

```

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