Merge pull request #48 from filecoin-project/types-messages

Review Messages

src/spec.md

@@ -36,29 +36,28 @@ In order to interact with other actors, they send messages between each other.
 
 ### Messages
 
-Messages describe the invocation of a method on another actor. 
+> _Messages_ describe the invocation of a method on an Actor. _Actors_ interact with each other by sending _messages_.
 
 #### Message
 
 An individual message has the following fields to represent this:
 
-- `Sender: ID ` - The actor who is sending this message.
-- `Receiver: ID` - The actor who is receving this message.
+- `Sender: ID ` - The actor who is sending the message.
+- `Receiver: ID` - The actor who is receving the message.
 - `MethodName: Symbol` - The method to be executed, must be an exported method on the contract of the `Receiver`.
 - `Parameters: []interface{}` - A list of parameters that are passed to the method.
 
-As it is required to meter all operations in the system there are also the two fields
+Messages are executed by the miners, some executions might be more expensive in terms of computation or storage than others. The execution of a message is priced by _gas_ in the following way:
 
 - `GasPrice: Amount` - The amount of Filecoin to be payed, per unit of _gas_ when sending this message.
 - `GasLimit: Gas`  - The maximum amount of gas that should be used when sending this message. Must be paid up-front, before any computation is done and can not be increased later.
 
-Lastly, to ensure that replay attacks can not happen there is a 
+Lastly, to ensure that replay attacks on messages can not happen, messages keep track of a counter:
 
-- `Counter`, which represents the number of messages sent from the `Sender`.
+- `Counter` - The number of messages sent from the `Sender`.
 
 #### Signed Message
-
-In addition messages need to be signed when sent from an actor that has a public - private key pair. Such messages are called _signed messages_ and have one additional field
+Messages need to be signed when sent from an actor that has a public - private key pair. Such messages are called _signed messages_ and have one additional field
 
 - `Signature: Signature` - The result of signing all fields of the message as described above using the private key of the `Sender`.