Merge branch 'fileSystem' of https://github.com/xiangli-cmu/etcd into fileSystem

Documentation/etcd-file-system.md

@@ -5,47 +5,60 @@
 ![alt text](./img/etcd_fs_structure.jpg "etcd file system structure")
 
 ## Node
-The building ingredients of etcd file system are two kinds of nodes -- files and directories:
-- File has data associated with it. 
-- Directory has children nodes associated with it.
+In **Etcd**, the **Node** is the rudimentary element constructing the whole.
+Currently **Etcd** file system is comprised in a Unix-like way of files and directories, and they are two kinds of nodes different in:
+
+- **File Node** has data associated with it.
+- **Directory Node** has children nodes associated with it.
+
+Besides the file and directory difference, all nodes have common attributes and operations as follows:
 
 ### Attributes:
-####Expiration Time [optional]
-The node will be deleted when it expires.
-####ACL
-The path of access control list of the node.
+- **Expiration Time** [optional]
+
+  The node will be deleted when it expires.
+
+- **ACL**
+
+  The path of access control list of the node.
 
 ### Operation:
-#### Get (path, recursive)
-Get the content of the node 
- - If the node is a file, the data of the file will be returned.
- - If the node is a directory, the child nodes of the directory will be returned. 
- - If recursive is true, it will recursively get the nodes of the directory.
-
-####Set (path, value[optional], ttl [optional])
-Set the value to a file. Set operation will help to create intermediate directories with no expiration time. 
- - If the value is given, set will create a file
- - If the value is not given, set will crate a directory
- - If ttl is given, the node will be deleted when it expires.
- 
-####Delete (path, recursive)
-Delete the node of given path.
- - If the node is a directory:
-  - If recursive is true, the operation will delete all nodes under the directory.
-  - If recursive is false, error will be returned.
-
-####TestAndSet (path, prevValue [prevIndex], value, ttl)
-Atomically test and set value to a file. If test succeeds, this operation will change the previous value of the file to the given value.
- - If the prevValue is given, it will test against previous value of the node.
-  - If the prevValue is empty, it will test if the node is not existing.
-  - If the prevValue is not empty, it will test if the prevValue is equal to the current value of the file.
- - If the prevIndex is given, it will test if the create/last modified index of the node is equal to prevIndex.
-
-####Renew (path, ttl)
-Set the node's expiration time to (current time + ttl)
+- **Get** (path, recursive)
+
+  Get the content of the node
+    - If the node is a file, the data of the file will be returned.
+    - If the node is a directory, the child nodes of the directory will be returned.
+    - If recursive is true, it will recursively get the nodes of the directory.
+
+- **Set** (path, value[optional], ttl [optional])
+
+  Set the value to a file. Set operation will help to create intermediate directories with no expiration time.
+    - If the value is given, set will create a file
+    - If the value is not given, set will crate a directory
+    - If ttl is given, the node will be deleted when it expires.
+
+- **Delete** (path, recursive)
+
+  Delete the node of given path.
+    - If the node is a directory:
+    - If recursive is true, the operation will delete all nodes under the directory.
+    - If recursive is false, error will be returned.
+
+- **TestAndSet** (path, prevValue [prevIndex], value, ttl)
+
+  Atomic *test and set* value to a file. If test succeeds, this operation will change the previous value of the file to the given value.
+    - If the prevValue is given, it will test against previous value of 
+    the node.
+    - If the prevValue is empty, it will test if the node is not existing.
+    - If the prevValue is not empty, it will test if the prevValue is equal to the current value of the file.
+    - If the prevIndex is given, it will test if the create/last modified index of the node is equal to prevIndex.
+
+- **Renew** (path, ttl)
+
+  Set the node's expiration time to (current time + ttl)
 
 ## ACL
 [TODO]
 
 ## User Group
-[TODO]
+[TODO]