Automatically merged updates to draft EIP(s) 777

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EIPS/eip-777.md

@@ -31,7 +31,7 @@ This standard tries to improve the widely used [ERC20] token standard. The main
 3. Both contracts and regular addresses can control and reject which token they receive by registering a `tokensReceived` hook. (Rejection is done by `revert`ing in the hook function.)
 4. The `tokensReceived` hook allows to send tokens to a contract and notify it in a single transaction, unlike [ERC20] which require a double call (`approve`/`transferFrom`) to achieve this.
 5. The token holder can "authorize" and "revoke" operators which can send tokens on their behalf. These operators are intended to be verified contracts such as an exchange, a cheque processor or an automatic charging system.
-6. Every token transaction contains a `data` bytes field and a similar `operatorData` to be used freely to pass data to the recipient.
+6. Every token transaction contains `data` and `operatorData` bytes fields to be used freely to pass data from the token holder and the operator, respectively.
 7. It is backward compatible with wallets that do not contain the `tokensReceived` hook function by deploying a proxy contract implementing the `tokensReceived` hook for the wallet.
 
 ## Specification
@@ -291,7 +291,7 @@ When an *operator* sends an `amount` of tokens from a *token holder* to a *recip
 - The balance of the *recipient* MUST be increased by the `amount`.
 - The balance of the *token holder* MUST be greater or equal to the `amount`—such that its resulting balance is greater or equal to zero (`0`) after the send.
 - The token contract MUST emit a `Sent` event with the correct values as defined in the [`Sent` Event][sent].
-- The *operator* MAY communicate any information in the `operatorData`.
+- The *operator* MAY include information in the `operatorData`.
 - The token contract MUST call the `tokensToSend` hook of the *token holder* if the *token holder* registers an `ERC777TokensSender` implementation via [ERC820].
 - The token contract MUST call the `tokensReceived` hook of the *recipient* if the *recipient* registers an `ERC777TokensRecipient` implementation via [ERC820].
 - The `data` and `operatorData` MUST be immutable during the entire send process—hence the same `data` and `operatorData` MUST be used to call both hooks and emit the `Sent` event.
@@ -322,7 +322,14 @@ The token contract MAY send tokens from many *token holders*, to many *recipient
 - The token contract MUST call the `tokensReceived` hook *after* updating the state.  
 I.e., `tokensToSend` MUST be called first, then the balances MUST be updated to reflect the send, and finally `tokensReceived` MUST be called *afterward*. Thus a `balanceOf` call within `tokensToSend` returns the balance of the address *before* the send and a `balanceOf` call within `tokensReceived` returns the balance of the address *after* the send.
 
-*NOTE*: The `data` field contains extra information intended for, and defined by the recipient— similar to the data field in a regular ether send transaction. Typically, `data` is used to describe the intent behind the send. The `operatorData` MUST only be provided by the *operator*. It is intended more for logging purposes and particular cases. (Examples include payment references, cheque numbers, countersignatures and more.) In most of the cases the recipient would ignore the `operatorData`, or at most, it would log the `operatorData`.
+*NOTE*: The `data` field contains information provided by the token holder—similar
+to the data field in a regular ether send transaction.
+The `tokensToSend()` hook, the `tokensReceived()`, or both 
+MAY use the information to decide if they wish to reject the transaction.
+
+*NOTE*: The `operatorData` field is analogous to the `data` field except it SHALL be provided by the *operator*.
+
+Typically, `data` is used to describe the intent behind the send. The `operatorData` MUST only be provided by the *operator*. It is intended more for logging purposes and particular cases. (Examples include payment references, cheque numbers, countersignatures and more.) In most of the cases the recipient would ignore the `operatorData`, or at most, it would log the `operatorData`.
 
 **`Sent` event** <a id="sent"></a>
 
@@ -339,8 +346,8 @@ Indicate a send of `amount` of tokens from the `from` address to the `to` addres
 > <small>`from`: Token holder.</small>  
 > <small>`to`: Token recipient.</small>  
 > <small>`amount`: Number of tokens to send.</small>  
-> <small>`data`: Information attached to the send, and intended for the recipient (`to`).</small>  
-> <small>`operatorData`: Information attached to the send by the `operator`.</small>
+> <small>`data`: Information provided by the *token holder*.</small>  
+> <small>`operatorData`: Information provided by the *operator*.</small>
 
 The `send` and `operatorSend` functions described below MUST be implemented to send tokens.
 Token contracts MAY implement other functions to send tokens.
@@ -360,7 +367,7 @@ The *operator* and the *token holder* MUST both be the `msg.sender`.
 > <small>**parameters**</small>  
 > <small>`to`: Token recipient.</small>  
 > <small>`amount`: Number of tokens to send.</small>  
-> <small>`data`: Information attached to the send, and intended for the recipient (`to`).</small>
+> <small>`data`: Information provided by the *token holder*.</small>
 
 **`operatorSend` function**
 
@@ -380,8 +387,8 @@ The *operator* MUST be `msg.sender`. The value of `from` MAY be `0x0`, then the
 > <small>`from`: Token holder (or `0x0` to set `from` to `msg.sender`).</small>  
 > <small>`to`: Token recipient.</small>  
 > <small>`amount`: Number of tokens to send.</small>  
-> <small>`data`: Information attached to the send, and intended for the recipient (`to`).</small>  
-> <small>`operatorData`: Information attached to the send by the `operator`.</small>
+> <small>`data`: Information provided by the *token holder*.</small>  
+> <small>`operatorData`: Information provided by the *operator*.</small>
 
 #### **Minting Tokens**
 
@@ -396,6 +403,7 @@ Nonetheless, the rules below MUST be respected when minting for a *recipient*:
 - The token contract MUST emit a `Minted` event with the correct values as defined in the [`Minted` Event][minted].
 - The token contract MUST call the `tokensReceived` hook of the *recipient* if the *recipient* registers an `ERC777TokensRecipient` implementation via [ERC820].
 - The `data` and `operatorData` MUST be immutable during the entire mint process&mdash;hence the same `data` and `operatorData` MUST be used to call the `tokensReceived` hook and emit the `Minted` event.
+- The `data` field MUST be empty.
 
 The token contract MUST `revert` when minting in any of the following cases:
 
@@ -418,7 +426,10 @@ The token contract MAY mint tokens for multiple *recipients* at once. In this ca
 
 *NOTE*: Minting an amount of zero (`0`) tokens is valid and MUST be treated as a regular mint.
 
-*NOTE*: The `data` field contains extra information intended for, and defined by the recipient&mdash; similar to the data field in a regular ether send transaction. Typically, `data` is used to describe the intent behind the mint. The `operatorData` MUST only be provided by the *operator*. It is intended more for logging purposes and particular cases. (Examples include payment references, cheque numbers, countersignatures and more.) In most of the cases the recipient would ignore the `operatorData`, or at most, it would log the `operatorData`.
+*NOTE*: The `operatorData` field contains information provided by the *operator*&mdash;similar
+to the data field in a regular ether send transaction. 
+The `tokensReceived()` hooks MAY use the information to decide if it wish to reject the transaction.
+
 
 **`Minted` event** <a id="minted"></a>
 
@@ -434,8 +445,8 @@ Indicate the minting of `amount` of tokens to the `to` address by the `operator`
 > <small>`operator`: Address which triggered the mint.</small>  
 > <small>`to`: Token recipient.</small>  
 > <small>`amount`: Number of tokens minted.</small>  
-> <small>`data`: Information attached to the minting, and intended for the recipient (`to`).</small>  
-> <small>`operatorData`: Information attached to the minting by the `operator`.</small>
+> <small>`data`: Information provided by the *token holder*.</small>  
+> <small>`operatorData`: Information provided by the *operator*.</small>
 
 #### **Burning Tokens**
 
@@ -450,7 +461,6 @@ The rules below MUST be respected when burning the tokens of a *token holder*:
 - The token contract MUST emit a `Burned` event with the correct values as defined in the [`Burned` Event][burned].
 - The token contract MUST call the `tokensToSend` hook of the *token holder* if the *token holder* registers an `ERC777TokensSender` implementation via [ERC820].
 - The `operatorData` MUST be immutable during the entire burn process&mdash;hence the same `operatorData` MUST be used to call the `tokensToSend` hook and emit the `Burned` event.
-- The `data` field of the `tokensToSend` hook MUST be empty.
 
 The token contract MUST `revert` when burning in any of the following cases:
 
@@ -491,8 +501,9 @@ Indicate the burning of `amount` of tokens from the `from` address by the `opera
 > <small>**parameters**</small>  
 > <small>`operator`: Address which triggered the burn.</small>  
 > <small>`from`: Token holder whose tokens are burned.</small>  
-> <small>`amount`: Number of tokens burned.</small>  
-> <small>`operatorData`: Information attached to the burn by the `operator`.</small>
+> <small>`amount`: Number of tokens burned.</small>
+> <small>`data`: Information provided by the *token holder*.</small>  
+> <small>`operatorData`: Information provided by the *operator*.</small>
 
 The `burn` and `operatorBurn` functions described below MUST be implemented to burn tokens.
 Token contracts MAY implement other functions to burn tokens.
@@ -526,7 +537,8 @@ The *operator* MUST be `msg.sender`. The value of `from` MAY be `0x0`, then the
 > <small>**parameters**</small>  
 > <small>`from`: Token holder whose tokens will be burned (or `0x0` to set `from` to `msg.sender`).</small>  
 > <small>`amount`: Number of tokens to burn.</small>  
-> <small>`operatorData`: Information attached to the burn by the *operator*.</small>
+> <small>`data`: Information provided by the *token holder*.</small>  
+> <small>`operatorData`: Information provided by the *operator*.</small>
 
 *NOTE*: The *operator* MAY pass any information via `operatorData`. The `operatorData` MUST only be provided by the *operator*.
 
@@ -566,8 +578,8 @@ Notify a send or burn (if `to` is `0x0`) of `amount` tokens from the `from` addr
 > <small>`from`: *token holder*.</small>  
 > <small>`to`: *token recipient* for a send and `0x` for a burn.</small>  
 > <small>`amount`: Number of tokens the *token holder* balance is decreased by.</small>  
-> <small>`data`: Extra information provided by the *token holder*.</small>  
-> <small>`operatorData`: Extra information provided by the address which triggered the balance decrease.</small>
+> <small>`data`: Information provided by the *token holder*.</small>  
+> <small>`operatorData`: Information provided by the *operator*.</small>
 
 The following rules apply when calling the `tokensToSend` hook:
 
@@ -579,7 +591,6 @@ The following rules apply when calling the `tokensToSend` hook:
 - `to` MUST be `0x0` for a burn.
 - `amount` MUST be the number of tokens the *token holder* balance is decreased by.
 - `data` MUST contain the extra information provided by the *token holder* (if any) for a send.
-- `data` MUST be empty for a burn.
 - `operatorData` MUST contain the extra information provided by the address which triggered the decrease of the balance (if any).
 - The *token holder* MAY block a decrease of its balance by `revert`ing. (I.e., reject the withdrawal of tokens from its account.)
 
@@ -629,8 +640,8 @@ Notify a send or mint (if `from` is `0x0`) of `amount` tokens from the `from` ad
 > <small>`from`: *token holder* for a send and `0x` for a mint.</small>  
 > <small>`to`: *token recipient*.</small>  
 > <small>`amount`: Number of tokens the *recipient* balance is increased by.</small>  
-> <small>`data`: Extra information provided by the *token holder* for a send and nothing (empty bytes) for a mint.</small>  
-> <small>`operatorData`: Extra information provided by the address which triggered the balance increase.</small>
+> <small>`data`: Information provided by the *token holder*.</small>
+> <small>`operatorData`: Information provided by the *operator*.</small>
 
 The following rules apply when calling the `tokensReceived` hook: