NEP: Non-fungible Token Standard

README.mediawiki

@@ -59,7 +59,7 @@ First review [[nep-1.mediawiki|NEP-1]]. Then clone the repository and add your N
 |-
 | [https://github.com/neo-project/proposals/pull/41 11]
 | Non-fungible Token Standard
-| Joe Stewart, Shane Mann
+| Joe Stewart, Shane Mann, Wyatt Mufson
 | Standard
 | Accepted
 |-
@@ -75,45 +75,45 @@ First review [[nep-1.mediawiki|NEP-1]]. Then clone the repository and add your N
 | Standard
 | Accepted
 |-
-| 
+|
 | Dynamic Sharding
-| 
+|
 | Standard
 | Stub
 |-
-| 
+|
 | Compact Block Relay
-| 
+|
 | Standard
 | Stub
 |-
-| 
+|
 | Peer Authentication
-| 
+|
 | Standard
 | Stub
 |-
-| 
+|
 | Aggregate Signature
-| 
+|
 | Standard
 | Stub
 |-
-| 
+|
 | Homomorphic Encryption
-| 
+|
 | Standard
 | Stub
 |-
-| 
+|
 | Zero-knowledge proof
-| 
+|
 | Standard
 | Stub
 |-
-| 
+|
 | Stealth Addresses
-| 
+|
 | Standard
 | Stub
 |}

nep-11.mediawiki

@@ -0,0 +1,242 @@
+<pre>
+  NEP: 11
+  Title: Non-Fungible Token Standard
+  Author: Joe Stewart <hal0x2328@splyse.tech>, Shane Mann <fetter@splyse.tech>, Wyatt Mufson <wyatt@ryu.games>
+  Type: Standard
+  Status: Accepted
+  Created: 2018-04-18
+</pre>
+
+==Abstract==
+
+This NEP defines a standard non-fungible token system for the NEO Smart Economy.
+
+==Motivation==
+
+NFTs are required to track, exchange and enforce ownership of digital assets.
+A non-fungible token (NFT) can be thought of like a property deed - each one is unique and carries some non-mutable information (e.g. the physical address of the property).
+Other information, such as the owner of the property, can be changed.
+Also, we provide built-in optional divisibility within each non-fungible asset.
+This allows for high value objects to be tokenized more effectively.
+
+==Specification==
+
+===Methods===
+
+====name====
+
+<pre>
+public static string name()
+</pre>
+
+Returns the name of the token. e.g. <code>"MyNFT"</code>.
+
+This method MUST always return the same value every time it is invoked.
+
+====symbol====
+
+<pre>
+public static string symbol()
+</pre>
+
+Returns a short string symbol of the token managed in this contract. e.g. <code>"MNFT"</code>.
+This symbol SHOULD be short (3-8 characters is recommended), with no whitespace characters or new-lines and SHOULD be limited to the uppercase latin alphabet (i.e. the 26 letters used in English).
+
+This method MUST always return the same value every time it is invoked.
+
+====totalSupply====
+
+<pre>
+public static BigInteger totalSupply()
+</pre>
+
+Returns the total token supply currently in the system.
+
+====decimals====
+
+<pre>
+public static byte decimals()
+</pre>
+
+Returns the number of decimals used by the token - e.g. <code>8</code>, means to divide the token amount by <code>100,000,000</code> to get its user representation.
+
+If the token managed in this contract is indivisible, the function SHOULD return <code>0</code>.
+
+If the function returns a non-zero value, all of the ''OPTIONAL'' methods in this standard MUST be implemented.
+
+This method MUST always return the same value every time it is invoked.
+
+====transfer====
+
+<pre>
+public static bool transfer(byte[] to, byte[] tokenid)
+</pre>
+
+This transfer method is for non-divisible NFTs <code>decimals() == 0</code>.
+It transfers the token with id <code>tokenid</code> to address <code>to</code>.
+
+The parameter <code>tokenid</code> SHOULD be a valid NFT.
+If not, this method SHOULD <code>throw</code> an exception.
+
+The parameter <code>to</code> SHOULD be a 20-byte address.
+If not, this method SHOULD <code>throw</code> an exception.
+
+The function SHOULD return <code>false</code> if the token that will be transferred has more than one owner.
+
+If the method succeeds, it MUST fire the <code>Transfer</code> event, and MUST return <code>true</code>, even if the token is sent to the owner.
+
+The function SHOULD check whether the owner address equals the caller contract hash.
+If so, the transfer SHOULD be processed; If not, the function SHOULD use the SYSCALL <code>Neo.Runtime.CheckWitness</code> to verify the transfer.
+
+If the <code>to</code> address is a deployed contract, the function SHOULD check the <code>payable</code> flag of this contract to decide whether it should transfer the tokens to this contract.
+
+If the transfer is not processed, the function SHOULD return <code>false</code>.
+
+<pre>
+public static bool transfer(byte[] from, byte[] to, BigInteger amount, byte[] tokenid)
+</pre>
+
+This transfer method is for divisible NFTs <code>decimals() > 0</code>.
+
+It transfers an <code>amount</code> of tokens with id <code>tokenid</code> from address <code>from</code> to address <code>to</code>.
+
+The parameter <code>tokenid</code> SHOULD be a valid NFT.
+If not, this method SHOULD <code>throw</code> an exception.
+
+The parameters <code>from</code> and <code>to</code> SHOULD be 20-byte addresses.
+If not, this method SHOULD <code>throw</code> an exception.
+
+The parameter <code>amount</code> SHOULD be greater than or equal to <code>0</code> and SHOULD be less than or equal to <code>pow(10, decimals())</code>.
+If not, this method SHOULD <code>throw</code> an exception.
+
+The function SHOULD return <code>false</code> if the <code>from</code> account balance does not have enough tokens to spend.
+
+If the method succeeds, it MUST fire the <code>Transfer</code> event, and MUST return <code>true</code>, even if the <code>amount</code> is <code>0</code>, or the token is sent to the owner.
+
+The function SHOULD check whether the <code>from</code> address equals the caller contract hash.
+If so, the transfer SHOULD be processed; If not, the function SHOULD use the SYSCALL <code>Neo.Runtime.CheckWitness</code> to verify the transfer.
+
+If the <code>to</code> address is a deployed contract, the function SHOULD check the <code>payable</code> flag of this contract to decide whether it should transfer the tokens to this contract.
+
+If the transfer is not processed, the function SHOULD return <code>false</code>.
+
+====ownerOf====
+
+<pre>
+public static enumerator ownerOf(byte[] tokenid)
+</pre>
+
+Returns an <code>enumerator</code> that contains all the co-owners that own the specified token.
+
+The parameter <code>tokenid</code> SHOULD be a valid NFT.
+If not, this method SHOULD <code>throw</code> an exception.
+
+====balanceOf====
+
+<pre>
+public static BigInteger balanceOf(byte[] owner)
+</pre>
+
+Returns the total amount of NFTs owned by the specified address.
+
+The parameter <code>owner</code> SHOULD be a 20-byte address.
+If not, this method SHOULD <code>throw</code> an exception.
+
+<pre>
+public static BigInteger balanceOf(byte[] owner, byte[] tokenid)
+</pre>
+
+If the second parameter <code>tokenid</code> is also provided, this method returns the balance of the specified token for the specified owner's account.
+
+The parameter <code>tokenid</code> SHOULD be a valid NFT.
+If not, this method SHOULD <code>throw</code> an exception.
+
+The parameter <code>owner</code> SHOULD be a 20-byte address.
+If not, this method SHOULD <code>throw</code> an exception.
+
+If the <code>owner</code> is an unused address, or it's not the owner of the specified token, this method SHOULD return <code>0</code>.
+
+====tokensOf====
+
+<pre>
+public static enumerator tokensOf(byte[] owner)
+</pre>
+
+Returns an <code>enumerator</code> that contains all of the token ids owned by the specified address.
+
+The parameter <code>owner</code> SHOULD be a 20-byte address.
+If not, this method SHOULD <code>throw</code> an exception.
+
+====properties====
+
+<pre>
+public static string properties(byte[] tokenid)
+</pre>
+
+Returns a serialized NVM object containing the properties for the given NFT.
+The NVM object must conform to the "NEO NFT Metadata JSON Schema".
+
+The parameter <code>tokenid</code> SHOULD be a valid NFT.
+If not, this method SHOULD <code>throw</code> an exception.
+
+====NEO NFT Metadata JSON Schema====
+
+Following is a description of the JSON Schema:
+<pre>
+{
+  "title": "Asset Metadata",
+  "type": "object",
+  "properties": {
+    "name": {
+      "type": "string",
+      "description": "Identifies the asset to which this NFT represents."
+    },
+    "description": {
+      "type": "string",
+      "description": "Describes the asset to which this NFT represents."
+    },
+    "image": {
+      "type": "string",
+      "description": "Optional. A URI pointing to a resource with mime type image/* representing the asset to which this NFT represents. Consider making any images at a width between 320 and 1080 pixels and aspect ratio between 1.91:1 and 4:5 inclusive."
+    },
+    "tokenURI": {
+      "type": "string",
+      "description": "Optional. A distinct URI for a given asset that adheres to RFC 3986"
+    }
+  }
+}
+</pre>
+
+Given this schema, the simplest json object that can be constructed is the following:
+<pre>
+{
+   "name": "Slime 1",
+   "description": "A slime"
+}
+</pre>
+
+And if all the properties are included:
+<pre>
+{
+   "name": "Slime 2",
+   "description": "A slime",
+   "image": "{some image URI}",
+   "tokenURI": "{some URI}"
+}
+</pre>
+
+===Events===
+
+====Transfer====
+
+<pre>
+public static event Transfer(byte[] from, byte[] to, BigInteger amount, byte[] tokenid)
+</pre>
+
+MUST trigger when tokens are transferred, including zero value transfers.
+
+A token contract which creates new tokens MUST trigger a <code>Transfer</code> event with the <code>from</code> address set to <code>null</code> when tokens are created.
+
+A token contract which burns tokens MUST trigger a <code>Transfer</code> event with the <code>to</code> address set to <code>null</code> when tokens are burned.
+
+==Implementation==