doc change(nn)

2 files changed, 34 insertions, 1 deletions

diff --git a/README.md b/README.md
index f825e57..6a0f1e4 100644
--- a/README.md
+++ b/README.md
@@ -36,7 +36,8 @@ The IO package is used to read and write parameters to file.
 The parameter package is used to store, read model parameters from file.
 * __[The Nerv Layer Package](doc/nerv_layer.md)__  
 The layer package is used to define propagation and backpropagation of different type of layers.
-
+* __[The Nerv NN Package](doc/nerv_nn.md)__  
+The nn package is for organizing a neural network, it contains __nerv.LayerRepo__, __nerv.ParamRepo__, and __nerv.DAGLayer__.
 [luaT]:https://github.com/torch/torch7/tree/master/lib/luaT
 [Torch]:https://github.com/torch
 [sync-help]:https://help.github.com/articles/syncing-a-fork/
diff --git a/doc/nerv_nn.md b/doc/nerv_nn.md
new file mode 100644
index 0000000..54c7165
--- /dev/null
+++ b/doc/nerv_nn.md
@@ -0,0 +1,32 @@
+#The Nerv NN Package#
+Part of the [Nerv](../README.md) toolkit.
+
+##Description##
+###Class hierarchy###
+it contains __nerv.LayerRepo__, __nerv.ParamRepo__, and __nerv.DAGLayer__(inherits __nerv.Layer__).
+
+###Class hierarchy and their members###
+* __nerv.ParamRepo__ Get parameter object by ID.  
+	* `table param_table` Contains the mapping of parameter ID to parameter file(__nerv.ChunkFile__) 
+*  __nerv.LayerRepo__ Get layer object by ID.  
+	* `table layers` Contains the mapping of layer ID to layer object.
+objects.
+* __nerv.DAGLayer__ inherits __nerv.Layer__.  
+
+##Methods##
+###__nerv.ParamRepo__###
+* __void ParamRepo:\_\_init(table param_files)__  
+`param_files` is a list of file names that stores parameters, the newed __ParamRepo__ will read them from file and store the mapping for future fetching.  
+* __nerv.Param ParamRepo.get_param(ParamRepo self, string pid, table global_conf)__  
+__ParamRepo__ will find the __nerv.ChunkFile__ `pf` that contains parameter of ID `pid` and return `pf:read_chunk(pid, global_conf)`.
+
+###__nerv.LayerRepo__###
+* __void LayerRepo:\_\_init(table layer_spec, ParamRepo param_repo, table global_conf)__  
+__LayerRepo__ will construct the layers specified in `layer_spec`. Every entry in the `layer_spec` table should follow the format below:  
+```
+layer_spec : {[layer_type1] = llist1, [layer_type2] = llist2, ...}
+llist : {layer1, layer2, ...}
+layer : layerid = {param_config, layer_config}
+param_config : {param1 = paramID1, param2 = paramID2}
+```
+__LayerRepo__ will merge `param_config` into `layer_config` and construct a layer by calling `layer_type(layerid, global_conf, layer_config)`.
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