A couple of years ago, when I tried to see how to model the class inheritance in json schema, I came out this example structure. The end json-schema, using descriminator, meets the requirement. It seems capable of competeting with normal OO language although it is a little bit verbose. But if using a nice UI to hide the verbose part by applying code-gen behind the scene, the target application can be very flexible.
To model the inheritance and correlated property placeToLive, here is the schema:
{
"$schema": "http://json-schema.org/schema#",
"type": "object",
"definitions": {
"WeightAndBreedable": {
"type": "object",
"properties": {
"breed": {
"type": "string"
},
"weight": {
"type": "number"
}
},
"required": [
"breed"
]
},
"PlaceToLive": {
"type": "object",
"properties": {
"__implType": {
"type": "string"
}
},
"required": [
"__implType"
]
},
"TreePlace": {
"allOf": [
{
"$ref": "#/definitions/PlaceToLive"
},
{
"type": "object",
"properties": {
"treeType": {
"type": "string"
},
"treePosition": {
"type": "string",
"enum": [
"middle",
"top",
"branch"
]
},
"__implType": {
"enum": [
"livingTree"
]
}
},
"required": [
"treePosition"
]
}
]
},
"RoomPlace": {
"allOf": [
{
"$ref": "#/definitions/PlaceToLive"
},
{
"type": "object",
"properties": {
"roomNum": {
"type": "string"
},
"roomSize": {
"type": "number"
},
"__implType": {
"enum": [
"livingRoom"
]
}
},
"required": [
"roomNum",
"roomSize"
]
}
]
},
"WaterPlace": {
"allOf": [
{
"$ref": "#/definitions/PlaceToLive"
},
{
"type": "object",
"properties": {
"salt": {
"type": "boolean"
},
"temperature": {
"type": "number"
},
"__implType": {
"enum": [
"livingWater"
]
}
},
"required": [
"salt",
"temperature"
]
}
]
},
"Animal": {
"properties": {
"name": {
"type": "string"
},
"dob": {
"type": "string",
"format": "date"
},
"spouse": {
"$ref": "#/definitions/Animal"
},
"placeToLive": {
"$ref": "#/definitions/PlaceToLive"
},
"__implType": {
"type": "string"
}
},
"required": [
"name",
"__implType"
]
},
"Dog": {
"allOf": [
{
"$ref": "#/definitions/Animal"
},
{
"$ref": "#/definitions/WeightAndBreedable"
},
{
"type": "object",
"properties": {
"barkOften": {
"type": "boolean"
},
"__implType": {
"enum": [
"Dog"
]
},
"spouse": {
"$ref": "#/definitions/Dog"
},
"placeToLive": {
"$ref": "#/definitions/RoomPlace"
}
},
"required": [
"barkOften"
]
}
]
},
"Cat": {
"allOf": [
{
"$ref": "#/definitions/Animal"
},
{
"type": "object",
"properties": {
"meowCount": {
"type": "number"
},
"__implType": {
"enum": [
"Cat"
]
},
"spouse": {
"$ref": "#/definitions/Cat"
},
"placeToLive": {
"$ref": "#/definitions/RoomPlace"
}
},
"required": [
"meowCount"
]
}
]
},
"Bird": {
"allOf": [
{
"$ref": "#/definitions/Animal"
},
{
"type": "object",
"properties": {
"flyHeight": {
"type": "number"
},
"originFrom": {
"type": "string"
},
"__implType": {
"enum": [
"Bird"
]
},
"spouse": {
"$ref": "#/definitions/Bird"
},
"placeToLive": {
"$ref": "#/definitions/TreePlace"
}
},
"required": [
"originFrom"
]
}
]
},
"Fish": {
"allOf": [
{
"$ref": "#/definitions/Animal"
},
{
"type": "object",
"properties": {
"swimmingALot": {
"type": "boolean"
},
"originFrom": {
"type": "string"
},
"__implType": {
"enum": [
"Fish"
]
},
"spouse": {
"$ref": "#/definitions/Fish"
},
"placeToLive": {
"$ref": "#/definitions/WaterPlace"
}
},
"required": [
"originFrom"
]
}
]
}
},
"oneOf": [
{
"$ref": "#/definitions/Dog"
},
{
"$ref": "#/definitions/Cat"
},
{
"$ref": "#/definitions/Fish"
},
{
"$ref": "#/definitions/Bird"
}
]
}Dog, Cat, Fish and Bird have common properties inside Animal, and each has different properties too. They can only have the same type Animal as their spouse. Their living place is also restricted at each specific type level. A valid example is:
{
"name": "Max",
"__implType": "Dog",
"breed": "Toy poodle",
"barkOften": true,
"spouse": {
"name": "Yellow",
"__implType": "Dog",
"breed": "Toy poodle",
"barkOften": false
},
"placeToLive": {
"__implType": "livingRoom",
"roomNum": "8A",
"roomSize": 100
}
}