From 651f9a93896a8b6f0d5df89c2ffb343507f7a0fd Mon Sep 17 00:00:00 2001
From: Superjom <superjom@gmail.com>
Date: Wed, 21 Jun 2017 18:22:51 +0800
Subject: [PATCH 1/2] add net_design doc

---
 doc/design/refactor_discuess/net_design.md | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
 create mode 100644 doc/design/refactor_discuess/net_design.md

diff --git a/doc/design/refactor_discuess/net_design.md b/doc/design/refactor_discuess/net_design.md
new file mode 100644
index 0000000000000..9d7c1724fe888
--- /dev/null
+++ b/doc/design/refactor_discuess/net_design.md
@@ -0,0 +1,14 @@
+# Overfiew
+
+整体设计上参考 caffe2的SimpleNet，即Net 是一组 operator 的集合，包含了operator相关的操作，比如Create, RunOps, Delete 等。
+
+Net 有如下一些特性：
+
+- Net 管理其拥有的operator
+- Net 本身不占用任何Variable资源
+- Net 的调用方式类似 Functor，即 `output = net(inputs, scope)` ，其中
+  - scope提供net执行所需要的全局Variable
+  - 输入一个或多个variable, `inputs`
+  - 返回一个variable, `output`
+
+# API

From d6f2abc8ed84e4c8748e8ed2164feaffa784fee4 Mon Sep 17 00:00:00 2001
From: Superjom <superjom@gmail.com>
Date: Wed, 21 Jun 2017 20:20:14 +0800
Subject: [PATCH 2/2] net design in en

---
 doc/design/refactor_discuess/net_design.md | 69 +++++++++++++++++++---
 1 file changed, 60 insertions(+), 9 deletions(-)

diff --git a/doc/design/refactor_discuess/net_design.md b/doc/design/refactor_discuess/net_design.md
index 9d7c1724fe888..86031cc0ae244 100644
--- a/doc/design/refactor_discuess/net_design.md
+++ b/doc/design/refactor_discuess/net_design.md
@@ -1,14 +1,65 @@
-# Overfiew
+# Network Design
 
-整体设计上参考 caffe2的SimpleNet，即Net 是一组 operator 的集合，包含了operator相关的操作，比如Create, RunOps, Delete 等。
+`Network` is the container and controller of a set of operators in a network, users can use `Network.addOp` to add operators into a network, 
+and use `Network.runOps` to run all the operators in the network.
 
-Net 有如下一些特性：
+The `Network` will
 
-- Net 管理其拥有的operator
-- Net 本身不占用任何Variable资源
-- Net 的调用方式类似 Functor，即 `output = net(inputs, scope)` ，其中
-  - scope提供net执行所需要的全局Variable
-  - 输入一个或多个variable, `inputs`
-  - 返回一个variable, `output`
+- manage all the operators contained in the network.
+- not own any `Variable`.
 
 # API
+
+To make the `Network` extendibe, a base class is defined like this
+
+```c++
+// The minimum a network should be implemented.
+class BaseNetwork {
+public:
+  BaseNetwork(const NetDef& def, Scope *scope);
+
+  // run all the operators and return success(true) or not.
+  virtual bool Run() = 0;
+
+protected:
+  // the input variables feed into the network.
+  std::vector<Variable*> external_inputs_;
+  // the corresponding output variables the network will write.
+  std::vector<Variable*> external_outputs_;
+  // scope which contains all the global variables visiable to this network.
+  Scope *scope_;
+};
+```
+
+A simple implemention is as followed:
+
+```c++
+class Network : public BaseNetwork {
+public:
+
+  // Create an empty network. 
+  Network(const std::string& name, Scope *scope);
+  
+  // NetDef is the definition of a network, in some occasion, operators are created 
+  // dynamically by user one by one; but in some other occasion such as LSTM, all 
+  // the operators in the networks should be  created during the construction 
+  // of the network. So a `NetDef` is provided to make the `Network` create a 
+  // network with all the operators described in `def`.
+  Network(const std::string& name, const NetDef& def, Scope *scope);
+  
+  // add a operator which is identified  as `type` and has attributes described
+  // in `attr`.
+  bool AddOp(const std::string &type, const OprAttr& attr);
+  
+  // run all operators in oprs_ sequentially.
+  virtual bool Run() override;
+  
+protected:
+  // to make the network's structure more human-readable, each network will 
+  // has a `name`
+  std::string name_;
+  // the operations are owned by `Network`.
+  std::vector<std::shared_ptr<Operator>> oprs_;
+};
+```
+