diff --git a/common/models.go b/common/models.go
index d2b283a..819132b 100644
--- a/common/models.go
+++ b/common/models.go
@@ -1,83 +1,95 @@
 package common
 
 import (
-	"github.com/jinzhu/gorm"
 	"github.com/jinzhu/gorm/dialects/postgres"
+	"time"
 )
 
+// Fields shared by all models (same as gorm.model but including proper json tags)
+type commonModelFields struct {
+	// ID of the model (primary key in DB)
+	ID uint `gorm:"primary_key",json:"id"`
+	// Time the model object is created
+	CreatedAt time.Time `json:"-"`
+	// Time of the last update of the model object
+	UpdatedAt time.Time `json:"-"`
+	// Time the model is deleted
+	DeletedAt *time.Time `json:"-"`
+}
+
 // User data model
 type User struct {
-	gorm.Model
+	commonModelFields
 	// Username of user
-	Username string `gorm:"unique;not null"`
+	Username string `gorm:"unique;not null",json:"username"`
 	// Password of user
-	Password string `gorm:"not null"`
+	Password string `gorm:"not null",json:"-"`
 	// Mail of user
-	Mail string `gorm:"default:''"`
+	Mail string `gorm:"default:''",json:"mail"`
 	// Role of user
-	Role string `gorm:"default:'user'"`
+	Role string `gorm:"default:'user'",json:"role"`
 	// Scenarios to which user has access
-	Scenarios []*Scenario `gorm:"many2many:user_scenarios"`
+	Scenarios []*Scenario `gorm:"many2many:user_scenarios",json:"-"`
 }
 
 // Scenario data model
 type Scenario struct {
-	gorm.Model
+	commonModelFields
 	// Name of scenario
-	Name string `gorm:"not null"`
+	Name string `gorm:"not null",json:"name"`
 	// Running state of scenario
-	Running bool `gorm:"default:false"`
+	Running bool `gorm:"default:false",json:"running"`
 	// Start parameters of scenario as JSON
-	StartParameters postgres.Jsonb
+	StartParameters postgres.Jsonb `json:"startParameters"`
 	// Users that have access to the scenario
-	Users []*User `gorm:"not null;many2many:user_scenarios"`
+	Users []*User `gorm:"not null;many2many:user_scenarios",json:"-"`
 	// SimulationModels that belong to the scenario
-	SimulationModels []SimulationModel `gorm:"foreignkey:ScenarioID"`
+	SimulationModels []SimulationModel `gorm:"foreignkey:ScenarioID",json:"-"`
 	// Dashboards that belong to the Scenario
-	Dashboards []Dashboard `gorm:"foreignkey:ScenarioID"`
+	Dashboards []Dashboard `gorm:"foreignkey:ScenarioID",json:"-"`
 }
 
 // SimulationModel data model
 type SimulationModel struct {
-	gorm.Model
+	commonModelFields
 	// Name of simulation model
-	Name string `gorm:"not null"`
+	Name string `gorm:"not null",json:"name"`
 	// Number of output signals
-	OutputLength int `gorm:"default:1"`
+	OutputLength int `gorm:"default:1",json:"outputLength"`
 	// Number of input signals
-	InputLength int `gorm:"default:1"`
+	InputLength int `gorm:"default:1",json:"inputLength"`
 	// Start parameters of simulation model as JSON
-	StartParameters postgres.Jsonb
+	StartParameters postgres.Jsonb `json:"startParameters"`
 	// ID of Scenario to which simulation model belongs
-	ScenarioID uint
+	ScenarioID uint `json:"scenarioID"`
 	// ID of simulator associated with simulation model
-	SimulatorID uint
+	SimulatorID uint `json:"simulatorID"`
 	// Mapping of output signals of the simulation model, order of signals is important
-	OutputMapping []Signal `gorm:"foreignkey:SimulationModelID"`
+	OutputMapping []Signal `gorm:"foreignkey:SimulationModelID",json:"-"`
 	// Mapping of input signals of the simulation model, order of signals is important
-	InputMapping []Signal `gorm:"foreignkey:SimulationModelID"`
+	InputMapping []Signal `gorm:"foreignkey:SimulationModelID",json:"-"`
 	// Files of simulation model (can be CIM and other simulation model file formats)
-	Files []File `gorm:"foreignkey:SimulationModelID"`
+	Files []File `gorm:"foreignkey:SimulationModelID",json:"-"`
 }
 
 // Signal data model
 type Signal struct {
-	gorm.Model
+	commonModelFields
 	// Name of Signal
-	Name string
+	Name string `json:"name"`
 	// Unit of Signal
-	Unit string
+	Unit string `json:"unit"`
 	// Index of the Signal in the mapping
-	Index uint
+	Index uint `json:"index"`
 	// Direction of the signal (in or out)
-	Direction string
+	Direction string `json:"direction"`
 	// ID of simulation model
-	SimulationModelID uint
+	SimulationModelID uint `json:"simulationModelID"`
 }
 
 // Simulator data model
 type Simulator struct {
-	gorm.Model
+	commonModelFields
 	// UUID of the simulator
 	UUID string `gorm:"not null",json:"uuid"`
 	// Host if the simulator
@@ -95,74 +107,74 @@ type Simulator struct {
 	// Raw properties of simulator as JSON string
 	RawProperties postgres.Jsonb `json:"rawProperties"`
 	// SimulationModels in which the simulator is used
-	SimulationModels []SimulationModel `gorm:"foreignkey:SimulatorID"`
+	SimulationModels []SimulationModel `gorm:"foreignkey:SimulatorID",json:"-"`
 }
 
 // Dashboard data model
 type Dashboard struct {
-	gorm.Model
+	commonModelFields
 	// Name of dashboard
-	Name string `gorm:"not null"`
+	Name string `gorm:"not null",json:"name"`
 	// Grid of dashboard
-	Grid int `gorm:"default:15"`
+	Grid int `gorm:"default:15",json:"grid"`
 	// ID of scenario to which dashboard belongs
-	ScenarioID uint
+	ScenarioID uint `json:"scenarioID"`
 	// Widgets that belong to dashboard
-	Widgets []Widget `gorm:"foreignkey:DashboardID"`
+	Widgets []Widget `gorm:"foreignkey:DashboardID",json:"-"`
 }
 
 // Widget data model
 type Widget struct {
-	gorm.Model
+	commonModelFields
 	// Name of widget
-	Name string `gorm:"not null"`
+	Name string `gorm:"not null",json:"name"`
 	// Type of widget
-	Type string `gorm:"not null"`
+	Type string `gorm:"not null",json:"type"`
 	// Width of widget
-	Width uint `gorm:"not null"`
+	Width uint `gorm:"not null",json:"width"`
 	// Height of widget
-	Height uint `gorm:"not null"`
+	Height uint `gorm:"not null",json:"height"`
 	// Minimal width of widget
-	MinWidth uint `gorm:"not null"`
+	MinWidth uint `gorm:"not null",json:"minWidth"`
 	// Minimal height of widget
-	MinHeight uint `gorm:"not null"`
+	MinHeight uint `gorm:"not null",json:"minHeight"`
 	// X position of widget
-	X int `gorm:"not null"`
+	X int `gorm:"not null",json:"x"`
 	// Y position of widget
-	Y int `gorm:"not null"`
+	Y int `gorm:"not null",json:"y"`
 	// Z position of widget
-	Z int `gorm:"not null"`
+	Z int `gorm:"not null",json:"z"`
 	// Locked state of widget
-	IsLocked bool `gorm:"default:false"`
+	IsLocked bool `gorm:"default:false",json:"isLocked"`
 	// Custom properties of widget as JSON string
-	CustomProperties postgres.Jsonb
+	CustomProperties postgres.Jsonb `json:"customProperties"`
 	// ID of dashboard to which widget belongs
-	DashboardID uint
+	DashboardID uint `json:"dashboardID"`
 	// Files that belong to widget (for example images)
-	Files []File `gorm:"foreignkey:WidgetID"`
+	Files []File `gorm:"foreignkey:WidgetID",json:"-"`
 }
 
 // File data model
 type File struct {
-	gorm.Model
+	commonModelFields
 	// Name of file
-	Name string `gorm:"not null"`
+	Name string `gorm:"not null",json:"name"`
 	// Type of file (MIME type)
-	Type string
+	Type string `json:"type"`
 	// Size of file (in byte)
-	Size uint
+	Size uint `json:"size"`
 	// Height of image (only needed in case of image)
-	ImageHeight uint
+	ImageHeight uint `json:"imageHeight"`
 	// Width of image (only needed in case of image)
-	ImageWidth uint
+	ImageWidth uint `json:"imageWidth"`
 	// Last modification time of file
-	Date string
+	Date string `json:"date"`
 	// ID of model to which file belongs
-	SimulationModelID uint
+	SimulationModelID uint `json:"simulationModelID"`
 	// ID of widget to which file belongs
-	WidgetID uint
+	WidgetID uint `json:"widgetID"`
 	// File itself
-	FileData []byte `gorm:"column:FileData"`
+	FileData []byte `gorm:"column:FileData",json:"-"`
 }
 
 // Credentials type (not for DB)