# bound-type-unknown

The **type of a bound** is neither `inclusive` nor `exclusive`.

- **Routes:** `read-events` and `observe-events`
- **Description:** `bound type is unknown: expected 'inclusive' or 'exclusive'`
- **Details:** **`bound`**, the bound whose type is unknown: `lowerBound`, or, when reading, `upperBound`. **`value`**, the type as the request gave it.

## Why It Happens

The **`type`** of a **[bound](/learn/tutorials/first-steps-with-eventsourcingdb/reading-events#reading-a-specific-range)** says whether the event with the bound's ID belongs to the range: `inclusive` includes it, `exclusive` leaves it out. No other value is accepted, and the values are **case-sensitive**, so `Inclusive` is refused, and so are words from other APIs, such as `closed`, `open`, or `gte`.

Before the type, the `id` of the bound is checked, and a bound without an `id`, or with one that is not a non-negative integer without a sign or a leading zero, is reported as **[`event-id-missing`](/docs/eventsourcingdb/errors/event-id-missing)** or **[`event-id-malformed`](/docs/eventsourcingdb/errors/event-id-malformed)**. A type that is left out or empty is reported as **[`bound-type-missing`](/docs/eventsourcingdb/errors/bound-type-missing)**. When reading, `lowerBound` is checked before `upperBound`.

## How to Fix It

Send the type in lowercase, as `inclusive` or `exclusive`. To resume after the last event you received, for example, use its ID with `exclusive`. Sending the same request again fails the same way.

## Example

To read the events of `/books/42` with a `lowerBound` of the type `after`, EventSourcingDB answers with this error, as a line of the stream, and then ends the stream with its `end` item:

```json
{
  "type": "error",
  "data": {
    "code": "https://docs.eventsourcingdb.io/errors/bound-type-unknown",
    "description": "bound type is unknown: expected 'inclusive' or 'exclusive'",
    "details": {
      "bound": "lowerBound",
      "value": "after"
    }
  }
}
```