> For the complete documentation index, see [llms.txt](https://docs.gopanacea.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.gopanacea.org/v2.0/specifications/aol.md).

# AOL

The AOL(Append Only Log), which can store various useful data such as healthcare data, is the key feature of the Panacea blockchain. It allows user to manage topics, authorities, and data.

### Overview

#### Create Topic

```go
// MsgCreateTopic - create topics
type MsgCreateTopic struct {
	TopicName    string         `json:"topic_name"`
	Description  string         `json:"description"`
	OwnerAddress sdk.AccAddress `json:"owner_address"`
}
```

A `MsgCreateTopic` is constructed to facilitate the AOL topic. Message sender can set a topic and description. The writer can add record after receiving the appropriate privileges.

Each field has limit. See the [Limits](#limits) section.

#### Add Writer

```go
// MsgAddWriter - add writer to the topic
type MsgAddWriter struct {
	TopicName     string         `json:"topic_name"`
	Moniker       string         `json:"moniker"`
	Description   string         `json:"description"`
	WriterAddress sdk.AccAddress `json:"writer_address"`
	OwnerAddress  sdk.AccAddress `json:"owner_address"`
}
```

The owner of the exist topics can manage writer privileges. Writer who received privileges from the topic owner can add record to the topic. This means that the owner authenticate the writer. This `MsgAddWriter` performs a function similar to issuing a certificate.

Each field has limit. See the [Limits](#limits) section.

#### Delete Writer

```go
// MsgDeleteWriter - delete writer from the topic
type MsgDeleteWriter struct {
	TopicName     string         `json:"topic_name"`
	WriterAddress sdk.AccAddress `json:"writer_address"`
	OwnerAddress  sdk.AccAddress `json:"owner_address"`
}
```

This `MsgDeleteWriter` removes writer from the topic. It is impossible to add record to the topic after being deprived of authority.

Each field has limit. See the [Limits](#limits) section.

#### Add Record

```go
// MsgAddRecord - add record to topic
type MsgAddRecord struct {
	TopicName       string         `json:"topic_name"`
	Key             []byte         `json:"key"`
	Value           []byte         `json:"value"`
	WriterAddress   sdk.AccAddress `json:"writer_address"`
	OwnerAddress    sdk.AccAddress `json:"owner_address"`
	FeePayerAddress sdk.AccAddress `json:"fee_payer_address"`
}
```

This `MsgAddRecord` add record or any data to the topic. If `FeePayerAddress` is provided, node charges fee to FeePayer.

Each field has limit. See the [Limits](#limits) section.

### Limits

| Field         | Min Length | Max Length | Charset                               |
| ------------- | ---------- | ---------- | ------------------------------------- |
| `TopicName`   | 1          | 70         | `a-z`, `A-Z`, `0-9`, `.`, `_` and `-` |
| `Moniker`     | 0          | 70         | `a-z`, `A-Z`, `0-9`, `.`, `_` and `-` |
| `Description` | 0          | 5,000      | Any                                   |
| `Key`         | 0          | 70         | Any                                   |
| `Value`       | 0          | 5,000      | Any                                   |


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.gopanacea.org/v2.0/specifications/aol.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.