The "read" condition consists of a string containing a rule that follows a subset of the [runes](https://pypi.org/project/runes/) language. Specifically only the `|`, `&`, `!`, `>`, `<`, and `=` operators are allowed. When the rule is an empty string it evaluates to `true`. When it consists of a single naked `"!"` it evaluates to `false`. The `#` specifically must not be interpreted as a comment, but always as a tag attribute. All the operatores must be tested against all possible values in the case of filter values that consist of lists of values and also in the case of event tags that can have multiple values for the same tag -- in other words, the `=` may be interpreted as a `values.any(v => v == runeValue)` instead of an `values == runeValue` operator; the `<` may be interpreted as a `values.any(v => v < runeValue)` and so on. In the case of events tags must also be identified by the `#` prefix, just like in filters.
The `read` rule operates on the values of the [NIP-01](01.md) **filter** object, while the `write` rule operates on the values of the **event** object.
When a `read` rule evaluates to `true` for a given **filter** the client SHOULD send a `REQ` message to the relay, otherwise it SHOULD NOT. When a `write` rule evaluates to `true` for a given **event** the client SHOULD send that event (in a `EVENT` message) to the relay, otherwise it MUST NOT.
### Examples
(Public keys are shortened to 3 characters for readability.)
- Rule evaluation examples:
- **read**
- for the filter `{"kinds": [0, 1, 2, 3], "authors": ["abcd", "1234"]}`
-`<empty>`: `true`
-`!`: `false`
-`authors=7890`: `false`
-`authors=7890|authors=1234`: `true`
-`authors=7890&authors=1234`: `false`
-`#e!`: `true`
-`#e=5555`: `false`
-`kinds=1|kinds=4`: `true`
-`kinds<2`: `true`
-`kinds>7`: `false`
- **write**
- for the event `{"kind": 7, "content": "banana", "tags": ["p", "6677"], "created_at": 123456789, "pubkey": "e3e3"}`
