# Book

Make Your Own Book

You can deploy your own Book on the Rinkeby network using our deployer (what are deployers?)

Deploy Your Own Book

Book contracts can be used with a dapp

Open Book Dapp

# Introduction

Book is a way to store information on the blockchain in an organized fashion. It has many uses:

  • Keep a catalog on the blockchain.
  • Manage organizational directives and use voting to effect changes to those directives.
  • Store content on the blockchain and have your users vote for modifications and new content.

# Organization

Each book consists of a list of Folders with names. Each folder then has a list of Files with content.

You can think of it like a filing cabinet, and one Book is essentially a drawer in a filing cabinet. It is similar to how files are organized on computers as well.

For example, here's what the Book for a charity working on improving water quality might look like:

 📁 Phone fundraising
  ├  🗎 Phone call opening speech
  └  🗎 Suggested donations
 📁 Initiatives
  ├  🗎 Clean Drinking Water
  └  🗎 Irrigation

Each file can have any kind of content, as long as the size of the file doesn't exceed about 14,000 characters. It could be plain text, structured data (such as JSON), binary data (for example a small image), and so on.

# Making Changes

Because all data on the blockchain is public, anyone can always read the contents of the files (unless it's encrypted). Making changes on the other hand can be restricted in several ways.

# A. Fully Open Mode

You can have the Book be fully open to making changes, which means anyone can create Folders and edit any Files. This is the default mode.

# B. Creator Editing Mode

This is like the Fully Open Mode, but after Files have been created, only the creator of the File can change it.

There is one exception: special users who are assigned as Editors can still make changes to any Files.

# C. Restricted Editing Mode

In this mode, normal users are not allowed to create Files or make changes. Instead, in order to make changes, a user must either be given the Editor role or hold a specific ERC-20 or ERC-721 token.

When using a token, you can make all Folders require the same token, or different Folders can require different tokens. Some Folders could also still be open to anyone to make changes.

For example, in our charity example, all Files under the "Phone fundraising" Folder could require you to have the "Fundraising Team Token" before you can make changes.

# D. Voting Only Mode

With this mode no one, not even Admins or Editors, can make changes directly to Files. Instead, any changes must go through a process of voting. See Voting below for details on how this works.

# Voting

Instead of making changes to Files directly, Book allows for Voting for changes to Files. Each File can have any number of Suggestions for its new content, and then those Suggestions can be voted on. The winning Suggestion will then replace the File and voting is closed.

Using the charity example from above, here's one possible scenario:

  • The charity's fundraising team wants to come up with a better opening speech for their phone fundraising efforts.
  • Anyone who has ever donated funds to the charity is allowed to create Suggestions for new or altered speeches, as well as anyone part of the organization.
  • Donors can then vote on the Suggestions.
  • After some time has passed, the Suggestion with the most votes replaces the current File, and the callers see the new opening speech.

After voting is complete, at any time a new round of voting can be started to replace the File again the same way. All vote counts and Suggestions are cleared between rounds.

Different parts of the process can be configured as follows.

# Who Can Create Suggestions

By default, anyone can create Suggestions for any File. There are two optional restrictions you can configure:

  • You can require that anyone creating a Suggestion must be a token holder of a specific token. For example, anyone who donated to our example charity would have a token to signify that they are a donor.
  • You can limit Suggestion creation to Writers. That means only users who you have specifically given the Writer role to can create them.


If you need more advanced controls, you can use a special ERC-20 token with its own rules to determine who gets to create Suggestions.

# Who Can Cast Votes

There are two options for who can cast votes. You can either keep voting open, allowing anyone to vote, or you can use a token like with creating Suggestions.

# What Is a Winning Suggestion

There are three ways you can configure which Suggestion will be selected:

  • Editor choice. Users you have given the Editor role will simply choose the winner. This is the default.
  • Voting winner. The Suggestion with the highest number of votes is selected as the new content. In case of ties, an Editor can choose between the tied Suggestions.
  • First past the post. The first Suggestion to reach a given number of votes is selected as the winner.

With Editor choice and Voting winner the File won't be changed until an Editor accepts the results. These are ideal for situations where the quantity of votes may vary, and you want to retain some amount of control.

With First past the post, the File will be changed immediately and automatically when the required number of votes is reached. This works well when you know how many people are voting, such as with a board or a committee.


With First past the post you can also set the number of votes required to be 1, and then it can act as content review that needs to be approved by someone else.

# Technical Details

# Folders

Each folder is identified by a unique name, and contains a list of files as well as the following additional data:

  • encoding holds information on the formatting of the content of the files. For example, this could be set to "json", in which case you know the files have JSON data.
  • metadata can hold any additional information on the contents of the Folder that you want to store that applies to all Files inside it.
  • accessToken can specify an ERC-20 or ERC-721 token that the user must have in order to have access to the Folder's Files. Note that access in this case can mean different things depending on the configuration of the Book, for details see Making Changes.

Both encoding and accessToken have default values in the Book itself that get applied to every new Folder. Only Admins can change the default values. Editors can modify them on existing Folders.


While Folders can't technically have other Folders inside them, you can still have a hierarchy of Folders by simply including it in the names of the Folders. For example, if the charity example from above has a Folder called Initiatives/Africa, that turns into a hierarchy:

 📁 Initiatives
  ├ 🗎 Clean Drinking Water
  ├ 🗎 Irrigation
  └ 📁 Africa
     └ 🗎 Rain Water Purification

# Files

Each File is stored on the blockchain as a string, which means it can naturally hold anything that can be turned into plain text.

In addition, the blockchain itself does not store a string and an array of bytes any differently, so as long as you treat it as such, the value can also be a byte array. This is where encoding and metadata are very useful.

There is not a specific limit to the size of a File, but in practice there is a limit to how much data you can assign at one time. This is due to the block gas limit, which is an upper limit on how much a transaction can do. This means the public blockchains can currently hold up to about 14,000 bytes.


The calculation to get the maximum size is fairly simple:

  • At time of writing, the gas limit for the Ethereum Main Network is 10 million.
  • The gas cost of data is paid in 32 byte chunks, with each chunk costing 20,000 gas.
  • You can reasonably expect to use up about 90% of the block gas limit and still be able to get the transaction to go through.

For text that uses ASCII characters (the normal English alphabet, numbers, punctuation), each character takes up exactly one byte, which means 14,000 characters.

International text and other special characters typically takes 2 bytes per character, so the size is reduced to about 7,000 characters. To learn more about how that works, read up on UTF-8 (opens new window).

# Using Tokens For Access Control

ERC-20 and ERC-721 tokens can be used to restrict some aspects of a Folder's Files. Tokens can be:

  • Required for making changes to Files.
  • Required for creating Suggestions.
  • Required for casting votes.

In these cases, when a Folder is configured to use a token, the user's balance of that token must be above 0. More specifically, the balanceOf function is called with the user's wallet address.

In addition, a token can be:

  • Used as the number of votes a user casts when they vote. This way you could give different users a different amount of say in voting.

In this case, the result of the balanceOf function for the user's wallet address is used as the number of votes they cast.

With an ERC-721, balanceOf will give the number of different tokens the user holds instead of a fungible balance, but it will work the same.


Strictly speaking the contract used for access control doesn't even need to be a token. It just needs to respond to balanceOf(address) with a number that makes sense.

# Encryption

While the contents of Files are publicly on the blockchain, you can still make them private by encrypting the contents. For this purpose, the Folder's encoding and metadata fields can be used to track the type of encryption used. You could directly store the type of algorithm being used, or you can just store some kind of identifier that will indicate to you which algorithm was used without revealing it publicly.

Encryption of the contents is an area Blockwell is actively working on, we will be adding more information on it in the near future.