JSON schema draft4 VS JSON schema draft3

Question

What are the features present in the schema draft 4 that are not in the JSON schema draft 3 produced by IETF ?

Answer 1

From the change logs:

New keywords

• anyOf (match at least one schema in the schema array),
• allOf (match all schemas in the schema array),
• oneOf (match exactly one schema in the schema array),
• not (do not match the schema),
• multipleOf (replaces divisibleBy),
• minProperties and maxProperties (the minimum and maximum number of members in an object instance),
• definitions (standardized container for inlined subschemas).

Removed:

• disallow
• extends
• divisbleBy

Changed in functionality:

Type

• When the value is an array, schemas are no longer allowed as elements. Also, the array must have at least one element.

Before

---

{
    "type": [ "string", { "other": "schema" } ]
}

Now

---

{
   "anyOf": [
       { "type": "string" },
       { "other": "schema" }
    ]
}

Required

• Before, it was an attribute of subschemas in properties. It is now a first level keyword playing the same role, and has a string array as an argument.

Before

---

{
    "properties": {
        "p": {
            "type": "string",
            "required": true
        },
        "q": {
            "type": "string",
            "required": true
        }
    }
}

Now

---

{
    "properties": {
        "p": { "type": "string" },
        "q": { "type": "string" }
    },
    "required": [ "p", "q" ]
}

Dependencies

• A single string in a property dependency is no longer allowed, only arrays are allowed

Before

---

{
    "dependencies": { "a": "b" }
}

Now

---

{
    "dependencies": { "a": [ "b" ] }
}

Answer 2

If you're interested in a deep dive, you can review a diff between the two drafts on the IETF site.

However, if you're looking for a simpler summary of changes, Geraint Luff and Francis Galiegue created a changelog page on the project's github wiki that lists the changes, additions, and removals.