diff --git a/dao/access_log.go b/dao/access_log.go
index 08c09ec4bb..6154330490 100644
--- a/dao/access_log.go
+++ b/dao/access_log.go
@@ -22,6 +22,7 @@ import (
 	"github.com/astaxie/beego/orm"
 )
 
+// AddAccessLog persists the access logs
 func AddAccessLog(accessLog models.AccessLog) error {
 	o := orm.NewOrm()
 	p, err := o.Raw(`insert into access_log
@@ -37,6 +38,7 @@ func AddAccessLog(accessLog models.AccessLog) error {
 	return err
 }
 
+//GetAccessLogs gets access logs according to different conditions
 func GetAccessLogs(accessLog models.AccessLog) ([]models.AccessLog, error) {
 
 	o := orm.NewOrm()
@@ -92,6 +94,7 @@ func GetAccessLogs(accessLog models.AccessLog) ([]models.AccessLog, error) {
 	return accessLogList, nil
 }
 
+// AccessLog ...
 func AccessLog(username, projectName, repoName, action string) error {
 	o := orm.NewOrm()
 	sql := "insert into  access_log (user_id, project_id, repo_name, operation, op_time) " +
diff --git a/dao/base.go b/dao/base.go
index 5a8735e842..0da51f181a 100644
--- a/dao/base.go
+++ b/dao/base.go
@@ -23,9 +23,10 @@ import (
 	"time"
 
 	"github.com/astaxie/beego/orm"
-	_ "github.com/go-sql-driver/mysql"
+	_ "github.com/go-sql-driver/mysql" //register mysql driver
 )
 
+// NonExistUserID : if a user does not exist, the ID of the user will be 0.
 const NonExistUserID = 0
 
 func isIllegalLength(s string, min int, max int) bool {
@@ -47,6 +48,7 @@ func isContainIllegalChar(s string, illegalChar []string) bool {
 	return false
 }
 
+// GenerateRandomString generates a random string
 func GenerateRandomString() (string, error) {
 	o := orm.NewOrm()
 	var uuid string
@@ -58,6 +60,7 @@ func GenerateRandomString() (string, error) {
 
 }
 
+//InitDB initializes the database
 func InitDB() {
 	orm.RegisterDriver("mysql", orm.DRMySQL)
 	addr := os.Getenv("MYSQL_HOST")
diff --git a/dao/item_detail.go b/dao/item_detail.go
index 1149cdcb9a..6504d77aac 100644
--- a/dao/item_detail.go
+++ b/dao/item_detail.go
@@ -20,6 +20,7 @@ import (
 	"github.com/astaxie/beego/orm"
 )
 
+// GetUserByProject gets all members of the project.
 func GetUserByProject(projectID int64, queryUser models.User) ([]models.User, error) {
 	o := orm.NewOrm()
 	u := []models.User{}
diff --git a/dao/project.go b/dao/project.go
index 118037acc2..7bec0c9df5 100644
--- a/dao/project.go
+++ b/dao/project.go
@@ -26,6 +26,8 @@ import (
 )
 
 //TODO:transaction, return err
+
+// AddProject adds a project to the database along with project roles information and access log records.
 func AddProject(project models.Project) error {
 
 	if isIllegalLength(project.Name, 4, 30) {
@@ -82,6 +84,7 @@ func AddProject(project models.Project) error {
 	return err
 }
 
+// IsProjectPublic ...
 func IsProjectPublic(projectName string) bool {
 	project, err := GetProjectByName(projectName)
 	if err != nil {
@@ -94,7 +97,7 @@ func IsProjectPublic(projectName string) bool {
 	return project.Public == 1
 }
 
-//Query the projects based on publicity and user, disregarding the names etc.
+// QueryProject querys the projects based on publicity and user, disregarding the names etc.
 func QueryProject(query models.Project) ([]models.Project, error) {
 	o := orm.NewOrm()
 
@@ -133,6 +136,7 @@ func QueryProject(query models.Project) ([]models.Project, error) {
 	return r, nil
 }
 
+//ProjectExists returns whether the project exists according to its name of ID.
 func ProjectExists(nameOrID interface{}) (bool, error) {
 	o := orm.NewOrm()
 	type dummy struct{}
@@ -155,6 +159,7 @@ func ProjectExists(nameOrID interface{}) (bool, error) {
 
 }
 
+// GetProjectByID ...
 func GetProjectByID(projectID int64) (*models.Project, error) {
 	o := orm.NewOrm()
 
@@ -175,6 +180,7 @@ func GetProjectByID(projectID int64) (*models.Project, error) {
 	}
 }
 
+// GetProjectByName ...
 func GetProjectByName(projectName string) (*models.Project, error) {
 	o := orm.NewOrm()
 	var p []models.Project
@@ -188,6 +194,7 @@ func GetProjectByName(projectName string) (*models.Project, error) {
 	}
 }
 
+// GetPermission gets roles that the user has according to the project.
 func GetPermission(username, projectName string) (string, error) {
 	o := orm.NewOrm()
 
@@ -209,6 +216,7 @@ func GetPermission(username, projectName string) (string, error) {
 	}
 }
 
+// ToggleProjectPublicity toggles the publicity of the project.
 func ToggleProjectPublicity(projectID int64, publicity int) error {
 	o := orm.NewOrm()
 	sql := "update project set public = ? where project_id = ?"
@@ -216,6 +224,7 @@ func ToggleProjectPublicity(projectID int64, publicity int) error {
 	return err
 }
 
+// QueryRelevantProjects returns all projects that the user is a member of.
 func QueryRelevantProjects(userID int) ([]models.Project, error) {
 	o := orm.NewOrm()
 	sql := `SELECT distinct p.project_id, p.name, p.public FROM registry.project p 
diff --git a/dao/project_role.go b/dao/project_role.go
index 752be77986..569cc3298e 100644
--- a/dao/project_role.go
+++ b/dao/project_role.go
@@ -20,6 +20,7 @@ import (
 	"github.com/astaxie/beego/orm"
 )
 
+// AddProjectRole ...
 func AddProjectRole(projectRole models.ProjectRole) (int64, error) {
 	o := orm.NewOrm()
 	p, err := o.Raw("insert into project_role (project_id, role_id) values (?, ?)").Prepare()
@@ -35,6 +36,7 @@ func AddProjectRole(projectRole models.ProjectRole) (int64, error) {
 	return id, err
 }
 
+// AddUserProjectRole inserts role information to table project_role and user_project_role.
 func AddUserProjectRole(userID int, projectID int64, roleID int) error {
 
 	o := orm.NewOrm()
@@ -76,6 +78,7 @@ func AddUserProjectRole(userID int, projectID int64, roleID int) error {
 	return err
 }
 
+// DeleteUserProjectRoles ...
 func DeleteUserProjectRoles(userID int, projectID int64) error {
 	o := orm.NewOrm()
 	sql := `delete from user_project_role where user_id = ? and pr_id in
diff --git a/dao/register.go b/dao/register.go
index 8ed6e2dd04..e42be0ce84 100644
--- a/dao/register.go
+++ b/dao/register.go
@@ -24,6 +24,7 @@ import (
 	"github.com/astaxie/beego/orm"
 )
 
+// Register is used for user to register, the password is encrypted before the record is inserted into database.
 func Register(user models.User) (int64, error) {
 
 	err := validate(user)
@@ -99,6 +100,7 @@ func validate(user models.User) error {
 	return nil
 }
 
+// UserExists returns whether a user exists according username or Email.
 func UserExists(user models.User, target string) (bool, error) {
 
 	if user.Username == "" && user.Email == "" {
diff --git a/dao/role.go b/dao/role.go
index b6d05421b2..ed5b693fb8 100644
--- a/dao/role.go
+++ b/dao/role.go
@@ -20,6 +20,7 @@ import (
 	"github.com/astaxie/beego/orm"
 )
 
+// GetUserProjectRoles returns roles that the user has according to the project.
 func GetUserProjectRoles(userQuery models.User, projectID int64) ([]models.Role, error) {
 
 	o := orm.NewOrm()
@@ -52,6 +53,7 @@ func GetUserProjectRoles(userQuery models.User, projectID int64) ([]models.Role,
 	return roleList, nil
 }
 
+// IsAdminRole returns whether the user  is admin.
 func IsAdminRole(userID int) (bool, error) {
 	//role_id == 1 means the user is system admin
 	userQuery := models.User{UserID: userID, RoleID: models.SYSADMIN}
diff --git a/dao/user.go b/dao/user.go
index ce3bc1bb3b..ef4468b6e6 100644
--- a/dao/user.go
+++ b/dao/user.go
@@ -25,6 +25,7 @@ import (
 	"github.com/astaxie/beego/orm"
 )
 
+// GetUser ...
 func GetUser(query models.User) (*models.User, error) {
 
 	o := orm.NewOrm()
@@ -65,6 +66,7 @@ func GetUser(query models.User) (*models.User, error) {
 	}
 }
 
+// LoginByDb is used for user to login with database auth mode.
 func LoginByDb(auth models.AuthModel) (*models.User, error) {
 
 	query := models.User{Username: auth.Principal, Email: auth.Principal}
@@ -84,6 +86,7 @@ func LoginByDb(auth models.AuthModel) (*models.User, error) {
 
 }
 
+// ListUsers lists all users according to different conditions.
 func ListUsers(query models.User) ([]models.User, error) {
 	o := orm.NewOrm()
 	u := []models.User{}
@@ -106,6 +109,7 @@ func ListUsers(query models.User) ([]models.User, error) {
 	return u, err
 }
 
+// ToggleUserAdminRole gives a user admim role.
 func ToggleUserAdminRole(u models.User) error {
 
 	projectRole := models.ProjectRole{PrID: 1} //admin project role
@@ -136,6 +140,7 @@ func ToggleUserAdminRole(u models.User) error {
 	return err
 }
 
+// ChangeUserPassword ...
 func ChangeUserPassword(u models.User, oldPassword ...string) error {
 	o := orm.NewOrm()
 	var err error
@@ -161,6 +166,7 @@ func ChangeUserPassword(u models.User, oldPassword ...string) error {
 	return err
 }
 
+// ResetUserPassword ...
 func ResetUserPassword(u models.User) error {
 	o := orm.NewOrm()
 	r, err := o.Raw(`update user set password=?, reset_uuid=? where reset_uuid=?`, utils.Encrypt(u.Password, u.Salt), "", u.ResetUUID).Exec()
@@ -177,12 +183,14 @@ func ResetUserPassword(u models.User) error {
 	return err
 }
 
+// UpdateUserResetUUID ...
 func UpdateUserResetUUID(u models.User) error {
 	o := orm.NewOrm()
 	_, err := o.Raw(`update user set reset_uuid=? where email=?`, u.ResetUUID, u.Email).Exec()
 	return err
 }
 
+// CheckUserPassword checks whether the password is correct.
 func CheckUserPassword(query models.User) (*models.User, error) {
 
 	currentUser, err := GetUser(query)
@@ -223,6 +231,7 @@ func CheckUserPassword(query models.User) (*models.User, error) {
 	}
 }
 
+// DeleteUser ...
 func DeleteUser(userID int) error {
 	o := orm.NewOrm()
 	_, err := o.Raw(`update user set deleted = 1 where user_id = ?`, userID).Exec()
diff --git a/models/access_log.go b/models/access_log.go
index 6894d34958..2cc8eca3cb 100644
--- a/models/access_log.go
+++ b/models/access_log.go
@@ -18,6 +18,7 @@ import (
 	"time"
 )
 
+// AccessLog holds information about logs which are used to record the actions that user take to the resourses.
 type AccessLog struct {
 	LogID     int       `orm:"column(log_id)" json:"LogId"`
 	UserID    int       `orm:"column(user_id)"  json:"UserId"`
diff --git a/models/auth_model.go b/models/auth_model.go
index e3ad853148..babc8dd3fd 100644
--- a/models/auth_model.go
+++ b/models/auth_model.go
@@ -1,19 +1,20 @@
 /*
-    Copyright (c) 2016 VMware, Inc. All Rights Reserved.
-    Licensed under the Apache License, Version 2.0 (the "License");
-    you may not use this file except in compliance with the License.
-    You may obtain a copy of the License at
-        
-        http://www.apache.org/licenses/LICENSE-2.0
-        
-    Unless required by applicable law or agreed to in writing, software
-    distributed under the License is distributed on an "AS IS" BASIS,
-    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-    See the License for the specific language governing permissions and
-    limitations under the License.
+   Copyright (c) 2016 VMware, Inc. All Rights Reserved.
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
 */
 package models
 
+// AuthModel holds information used to authenticate.
 type AuthModel struct {
 	Principal string
 	Password  string
diff --git a/models/notification.go b/models/notification.go
index 6c2933bf7d..f5fab61db3 100644
--- a/models/notification.go
+++ b/models/notification.go
@@ -18,10 +18,12 @@ import (
 	"time"
 )
 
+// Notification holds all events.
 type Notification struct {
 	Events []Event
 }
 
+// Event holds the details of a event.
 type Event struct {
 	ID        string `json:"Id"`
 	TimeStamp time.Time
@@ -31,6 +33,7 @@ type Event struct {
 	Actor     *Actor
 }
 
+// Target holds information about the target of a event.
 type Target struct {
 	MediaType  string
 	Digest     string
@@ -38,10 +41,12 @@ type Target struct {
 	URL        string `json:"Url"`
 }
 
+// Actor holds information about actor.
 type Actor struct {
 	Name string
 }
 
+// Request holds information about a request.
 type Request struct {
 	ID        string `json:"Id"`
 	Method    string
diff --git a/models/project.go b/models/project.go
index 5ff4584ac0..9673191277 100644
--- a/models/project.go
+++ b/models/project.go
@@ -18,6 +18,7 @@ import (
 	"time"
 )
 
+// Project holds the details of a project.
 type Project struct {
 	ProjectID       int64     `orm:"column(project_id)" json:"ProjectId"`
 	OwnerID         int       `orm:"column(owner_id)" json:"OwnerId"`
diff --git a/models/project_role.go b/models/project_role.go
index 88da32d6a1..a536b08195 100644
--- a/models/project_role.go
+++ b/models/project_role.go
@@ -14,6 +14,7 @@
 */
 package models
 
+// ProjectRole holds information about the relationship of project and role.
 type ProjectRole struct {
 	PrID      int   `orm:"column(pr_id)" json:"PrId"`
 	ProjectID int64 `orm:"column(project_id)" json:"ProjectId"`
diff --git a/models/repo.go b/models/repo.go
index d17293e437..c12d5b23c8 100644
--- a/models/repo.go
+++ b/models/repo.go
@@ -14,12 +14,7 @@
 */
 package models
 
-type V1Repo struct {
-	NumResults int
-	Query      string
-	Results    []RepoItem
-}
-
+// Repo holds information about repositories.
 type Repo struct {
 	Repositories []string `json:"repositories"`
 }
diff --git a/models/repo_item.go b/models/repo_item.go
index 380a714552..0c3b78f658 100644
--- a/models/repo_item.go
+++ b/models/repo_item.go
@@ -18,6 +18,7 @@ import (
 	"time"
 )
 
+// RepoItem holds manifest of an image.
 type RepoItem struct {
 	ID            string    `json:"Id"`
 	Parent        string    `json:"Parent"`
diff --git a/models/role.go b/models/role.go
index 0ebbe52fc7..5cacbef9f1 100644
--- a/models/role.go
+++ b/models/role.go
@@ -15,12 +15,17 @@
 package models
 
 const (
-	SYSADMIN     = 1
+	//SYSADMIN system administrator
+	SYSADMIN = 1
+	//PROJECTADMIN project administrator
 	PROJECTADMIN = 2
-	DEVELOPER    = 3
-	GUEST        = 4
+	//DEVELOPER developer
+	DEVELOPER = 3
+	//GUEST guest
+	GUEST = 4
 )
 
+// Role holds the details of a role.
 type Role struct {
 	RoleID   int    `json:"role_id" orm:"column(role_id)"`
 	RoleCode string `json:"role_code" orm:"column(role_code)"`
diff --git a/models/tag.go b/models/tag.go
index 50ea314705..748efaa107 100644
--- a/models/tag.go
+++ b/models/tag.go
@@ -14,6 +14,7 @@
 */
 package models
 
+// Tag holds information about a tag.
 type Tag struct {
 	Version string `json:"version"`
 	ImageID string `json:"image_id"`
diff --git a/models/user.go b/models/user.go
index 8640c878a1..572a5a449e 100644
--- a/models/user.go
+++ b/models/user.go
@@ -14,6 +14,7 @@
 */
 package models
 
+// User holds the details of a user.
 type User struct {
 	UserID       int    `orm:"column(user_id)" json:"UserId"`
 	Username     string `orm:"column(username)"`
diff --git a/models/user_project_role.go b/models/user_project_role.go
index d6e52d1e09..d0dd366529 100644
--- a/models/user_project_role.go
+++ b/models/user_project_role.go
@@ -14,6 +14,7 @@
 */
 package models
 
+// UserProjectRole holds information about relationship of user, project and role.
 type UserProjectRole struct {
 	UprID  int   `orm:"column(upr_id)" json:"UprId"`
 	UserID int   `orm:"column(user_id)" json:"UserId"`
diff --git a/utils/encrypt.go b/utils/encrypt.go
index f97dc53dbb..4def9095c2 100644
--- a/utils/encrypt.go
+++ b/utils/encrypt.go
@@ -1,16 +1,16 @@
 /*
-    Copyright (c) 2016 VMware, Inc. All Rights Reserved.
-    Licensed under the Apache License, Version 2.0 (the "License");
-    you may not use this file except in compliance with the License.
-    You may obtain a copy of the License at
-        
-        http://www.apache.org/licenses/LICENSE-2.0
-        
-    Unless required by applicable law or agreed to in writing, software
-    distributed under the License is distributed on an "AS IS" BASIS,
-    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-    See the License for the specific language governing permissions and
-    limitations under the License.
+   Copyright (c) 2016 VMware, Inc. All Rights Reserved.
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
 */
 package utils
 
@@ -21,6 +21,7 @@ import (
 	"golang.org/x/crypto/pbkdf2"
 )
 
+// Encrypt encrypts the content with salt
 func Encrypt(content string, salt string) string {
 	return fmt.Sprintf("%x", pbkdf2.Key([]byte(content), []byte(salt), 4096, 16, sha1.New))
 }
diff --git a/utils/mail.go b/utils/mail.go
index 8fc0c02f06..e9c3972dc9 100644
--- a/utils/mail.go
+++ b/utils/mail.go
@@ -1,16 +1,16 @@
 /*
-    Copyright (c) 2016 VMware, Inc. All Rights Reserved.
-    Licensed under the Apache License, Version 2.0 (the "License");
-    you may not use this file except in compliance with the License.
-    You may obtain a copy of the License at
-        
-        http://www.apache.org/licenses/LICENSE-2.0
-        
-    Unless required by applicable law or agreed to in writing, software
-    distributed under the License is distributed on an "AS IS" BASIS,
-    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-    See the License for the specific language governing permissions and
-    limitations under the License.
+   Copyright (c) 2016 VMware, Inc. All Rights Reserved.
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
 */
 package utils
 
@@ -23,12 +23,15 @@ import (
 	"github.com/astaxie/beego"
 )
 
+// Mail holds information about content of Email
 type Mail struct {
 	From    string
 	To      []string
 	Subject string
 	Message string
 }
+
+// MailConfig holds information about Email configurations
 type MailConfig struct {
 	Identity string
 	Host     string
@@ -39,6 +42,7 @@ type MailConfig struct {
 
 var mc MailConfig
 
+// SendMail sends Email according to the configurations
 func (m Mail) SendMail() error {
 
 	if mc.Host == "" {
diff --git a/utils/registry_utils.go b/utils/registry_utils.go
index c7ac9c6136..4656aad199 100644
--- a/utils/registry_utils.go
+++ b/utils/registry_utils.go
@@ -29,6 +29,7 @@ import (
 
 const sessionCookie = "beegosessionID"
 
+// BuildRegistryURL builds the URL of registry
 func BuildRegistryURL(segments ...string) string {
 	registryURL := os.Getenv("REGISTRY_URL")
 	if registryURL == "" {
@@ -45,6 +46,7 @@ func BuildRegistryURL(segments ...string) string {
 	return url
 }
 
+// HTTPGet is used to call the API of registry. If a token is needed, it will get a token first.
 func HTTPGet(URL, sessionID, username, password string) ([]byte, error) {
 	response, err := http.Get(URL)
 	if err != nil {
diff --git a/utils/utils.go b/utils/utils.go
index 96260311ba..0fcda16c43 100644
--- a/utils/utils.go
+++ b/utils/utils.go
@@ -23,10 +23,12 @@ import (
 	"github.com/astaxie/beego"
 )
 
+// Repository holds information about repository
 type Repository struct {
 	Name string
 }
 
+// ParseBasicAuth parses the basic authorization
 func ParseBasicAuth(authorization []string) (username, password string) {
 	if authorization == nil || len(authorization) == 0 {
 		beego.Debug("Authorization header is not set.")
@@ -38,6 +40,7 @@ func ParseBasicAuth(authorization []string) (username, password string) {
 	return pair[0], pair[1]
 }
 
+// GetProject parses the repository and return the name of project.
 func (r *Repository) GetProject() string {
 	if !strings.ContainsRune(r.Name, '/') {
 		return ""
@@ -45,18 +48,22 @@ func (r *Repository) GetProject() string {
 	return r.Name[0:strings.LastIndex(r.Name, "/")]
 }
 
+// ProjectSorter holds an array of projects
 type ProjectSorter struct {
 	Projects []models.Project
 }
 
+// Len returns the length of array in ProjectSorter
 func (ps *ProjectSorter) Len() int {
 	return len(ps.Projects)
 }
 
+// Less defines the comparison rules of project
 func (ps *ProjectSorter) Less(i, j int) bool {
 	return ps.Projects[i].Name < ps.Projects[j].Name
 }
 
+// Swap swaps the position of i and j
 func (ps *ProjectSorter) Swap(i, j int) {
 	ps.Projects[i], ps.Projects[j] = ps.Projects[j], ps.Projects[i]
 }