diff --git a/README.md b/README.md
index c8fba7541..367d07af1 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-Gogs - Go Git Service
+Gogs - Go Git Service [![Go Walker](http://gowalker.org/api/v1/badge)](https://gowalker.org/github.com/gogits/gogs)
 =====================
 
 Gogs(Go Git Service) is a GitHub-like clone in the Go Programming Language.
@@ -7,6 +7,17 @@ Gogs(Go Git Service) is a GitHub-like clone in the Go Programming Language.
 
 There are some very good products in this category such as [gitlab](http://gitlab.com), but the environment setup steps often make us crazy. So our goal of Gogs is to build a GitHub-like clone with very easy setup steps, which take advantages of the Go Programming Language.
 
+## Overview
+
+Please see [Wiki](https://github.com/gogits/gogs/wiki) for project design.
+
+## Installation
+
+### Dependencies
+
+- [Go Programming Language](http://golang.org): Main develop language.
+- [libgit2](http://libgit2.github.com/): Git data manipulation.
+
 ## Acknowledgments
 
 - Logo inspired by [martini](https://github.com/martini-contrib).
diff --git a/models/models.go b/models/models.go
index bddece474..1c8ce7301 100644
--- a/models/models.go
+++ b/models/models.go
@@ -11,10 +11,8 @@ import (
 )
 
 var (
-	// orm
-	orm *xorm.Engine
-	// repository root path
-	root string
+	orm          *xorm.Engine
+	repoRootPath string
 )
 
 type PublicKey struct {
diff --git a/models/models_test.go b/models/models_test.go
index f4a40ff32..c44ef476c 100644
--- a/models/models_test.go
+++ b/models/models_test.go
@@ -1,3 +1,7 @@
+// Copyright 2014 The Gogs Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
 package models
 
 import (
diff --git a/models/repo.go b/models/repo.go
index 8e3aae9ab..485eee89f 100644
--- a/models/repo.go
+++ b/models/repo.go
@@ -1,3 +1,7 @@
+// Copyright 2014 The Gogs Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
 package models
 
 import (
@@ -33,7 +37,7 @@ func IsRepositoryExist(user *User, reposName string) (bool, error) {
 // create a repository for a user or orgnaziation
 //
 func CreateRepository(user *User, reposName string) (*Repo, error) {
-	p := filepath.Join(root, user.Name)
+	p := filepath.Join(repoRootPath, user.Name)
 	os.MkdirAll(p, os.ModePerm)
 	f := filepath.Join(p, reposName)
 	_, err := git.InitRepository(f, false)
@@ -89,29 +93,22 @@ func UnWatchRepository() {
 
 }
 
-//
-// delete a repository for a user or orgnaztion
-//
-func DeleteRepository(user *User, reposName string) error {
+// DeleteRepository deletes a repository for a user or orgnaztion.
+func DeleteRepository(user *User, reposName string) (err error) {
 	session := orm.NewSession()
-	_, err := session.Delete(&Repo{OwnerId: user.Id, Name: reposName})
-	if err != nil {
+	if _, err = session.Delete(&Repo{OwnerId: user.Id, Name: reposName}); err != nil {
 		session.Rollback()
 		return err
 	}
-	_, err = session.Exec("update user set num_repos = num_repos - 1 where id = ?", user.Id)
-	if err != nil {
+	if _, err = session.Exec("update user set num_repos = num_repos - 1 where id = ?", user.Id); err != nil {
 		session.Rollback()
 		return err
 	}
-	err = session.Commit()
-	if err != nil {
+	if err = session.Commit(); err != nil {
 		session.Rollback()
 		return err
 	}
-
-	err = os.RemoveAll(filepath.Join(root, user.Name, reposName))
-	if err != nil {
+	if err = os.RemoveAll(filepath.Join(repoRootPath, user.Name, reposName)); err != nil {
 		// TODO: log and delete manully
 		return err
 	}
diff --git a/models/user.go b/models/user.go
index 4093c5ccc..6ea329c52 100644
--- a/models/user.go
+++ b/models/user.go
@@ -1,3 +1,7 @@
+// Copyright 2014 The Gogs Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
 package models
 
 import (
@@ -7,18 +11,21 @@ import (
 	"time"
 
 	"github.com/dchest/scrypt"
-) // user type
+)
+
+// User types.
 const (
-	Individual = iota + 1
-	Organization
+	UT_INDIVIDUAL = iota + 1
+	UT_ORGANIZATION
 )
 
-// login type
+// Login types.
 const (
-	Plain = iota + 1
-	LDAP
+	LT_PLAIN = iota + 1
+	LT_LDAP
 )
 
+// A User represents the object of individual and member of organization.
 type User struct {
 	Id            int64
 	LowerName     string `xorm:"unique not null"`
@@ -36,6 +43,7 @@ type User struct {
 	Updated       time.Time `xorm:"updated"`
 }
 
+// A Follow represents
 type Follow struct {
 	Id       int64
 	UserId   int64     `xorm:"unique(s)"`
@@ -43,15 +51,17 @@ type Follow struct {
 	Created  time.Time `xorm:"created"`
 }
 
+// Operation types of repository.
 const (
-	OpCreateRepo = iota + 1
-	OpDeleteRepo
-	OpStarRepo
-	OpFollowRepo
-	OpCommitRepo
-	OpPullRequest
+	OP_CREATE_REPO = iota + 1
+	OP_DELETE_REPO
+	OP_STAR_REPO
+	OP_FOLLOW_REPO
+	OP_COMMIT_REPO
+	OP_PULL_REQUEST
 )
 
+// A Action represents
 type Action struct {
 	Id      int64
 	UserId  int64
@@ -62,34 +72,61 @@ type Action struct {
 }
 
 var (
-	ErrUserNotExist = errors.New("User not exist")
+	ErrUserAlreadyExist = errors.New("User already exist")
+	ErrUserNotExist     = errors.New("User does not exist")
 )
 
-// user's name should be noncased unique
+// IsUserExist checks if given user name exist,
+// the user name should be noncased unique.
 func IsUserExist(name string) (bool, error) {
 	return orm.Get(&User{LowerName: strings.ToLower(name)})
 }
 
-func RegisterUser(user *User) error {
-	_, err := orm.Insert(user)
+// validateUser checks if user exist.
+func validateUser(name string) error {
+	isExist, err := IsUserExist(name)
+	if err != nil {
+		return err
+	} else if isExist {
+		return ErrUserAlreadyExist
+	}
+	return nil
+}
+
+// RegisterUser creates record of a new user.
+func RegisterUser(user *User) (err error) {
+	if err = validateUser(user.Name); err != nil {
+		return err
+	}
+	_, err = orm.Insert(user)
 	return err
 }
 
-func UpdateUser(user *User) error {
-	_, err := orm.Id(user.Id).Update(user)
+// UpdateUser updates user's information.
+func UpdateUser(user *User) (err error) {
+	_, err = orm.Id(user.Id).Update(user)
 	return err
 }
 
+// DeleteUser completely deletes everything of the user.
+func DeleteUser(user *User) error {
+	// TODO: check if has ownership of any repository.
+	_, err := orm.Delete(user)
+	// TODO: delete and update follower information.
+	return err
+}
+
+// EncodePasswd encodes password to safe format.
 func (user *User) EncodePasswd(pass string) error {
 	newPasswd, err := scrypt.Key([]byte(user.Passwd), []byte("!#@FDEWREWR&*("), 16384, 8, 1, 64)
 	user.Passwd = fmt.Sprintf("%x", newPasswd)
 	return err
 }
 
+// LoginUserPlain validates user by raw user name and password.
 func LoginUserPlain(name, passwd string) (*User, error) {
 	user := User{Name: name}
-	err := user.EncodePasswd(passwd)
-	if err != nil {
+	if err := user.EncodePasswd(passwd); err != nil {
 		return nil, err
 	}
 
@@ -103,6 +140,7 @@ func LoginUserPlain(name, passwd string) (*User, error) {
 	return &user, nil
 }
 
+// FollowUser marks someone be another's follower.
 func FollowUser(userId int64, followId int64) error {
 	session := orm.NewSession()
 	defer session.Close()
@@ -125,6 +163,7 @@ func FollowUser(userId int64, followId int64) error {
 	return session.Commit()
 }
 
+// UnFollowUser unmarks someone be another's follower.
 func UnFollowUser(userId int64, unFollowId int64) error {
 	session := orm.NewSession()
 	defer session.Close()