jsonschema-validation.xml

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<rfc category="info" docName="draft-wright-json-schema-validation-02" ipr="trust200902">
    <front>
        <title abbrev="JSON Schema Validation">
            JSON Schema Validation: A Vocabulary for Structural Validation of JSON
        </title>

        <author fullname="Austin Wright" initials="A" surname="Wright" role="editor">
            <address>
                <email>aaa@bzfx.net</email>
            </address>
        </author>

        <author fullname="Geraint Luff" initials="G" surname="Luff">
            <address>
                <email>luffgd@gmail.com</email>
            </address>
        </author>

        <author fullname="Henry Andrews" initials="H" surname="Andrews" role="editor">
            <organization>Cloudflare, Inc.</organization>
            <address>
                <email>henry@cloudflare.com</email>
            </address>
        </author>

        <date year="2017"/>
        <workgroup>Internet Engineering Task Force</workgroup>
        <keyword>JSON</keyword>
        <keyword>Schema</keyword>
        <keyword>validation</keyword>

        <abstract>
            <t>
                JSON Schema (application/schema+json) has several purposes, one of which is JSON
                instance validation.
                This document specifies a vocabulary for JSON Schema to describe the meaning of JSON
                documents, provide hints for user interfaces working with JSON data, and to make
                assertions about what a valid document must look like.
            </t>
        </abstract>

        <note title="Note to Readers">
            <t>
                The issues list for this draft can be found at
                <eref target="https://github.com/json-schema-org/json-schema-spec/issues"/>.
            </t>
            <t>
                For additional information, see <eref target="http://json-schema.org/"/>.
            </t>
            <t>
                To provide feedback, use this issue tracker, the communication methods listed on the
                homepage, or email the document editors.
            </t>
        </note>
    </front>

    <middle>
        <section title="Introduction">
            <t>
                JSON Schema can be used to require that a given JSON document (an instance)
                satisfies a certain number of criteria. These criteria are asserted by using
                keywords described in this specification. In addition, a set of keywords
                is also defined to assist in interactive user interface instance generation.
            </t>
            <t>
                This specification will use the concepts, syntax, and terminology defined
                by the <xref target="json-schema">JSON Schema core</xref> specification.
            </t>
        </section>

        <section title="Conventions and Terminology">
            <t>
                <!-- The text in this section has been copied from the official boilerplate,
                and should not be modified.-->

                The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
                "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
                interpreted as described in <xref target="RFC2119">RFC 2119</xref>.
            </t>
            <t>
                This specification uses the term "container instance" to refer to both array and
                object instances. It uses the term "children instances" to refer to array elements
                or object member values.
            </t>
            <t>
                Elements in an array value are said to be unique if no two elements of this array
                are <xref target="json-schema">equal</xref>.
            </t>
        </section>

        <section title="Interoperability considerations">

            <section title="Validation of string instances">
                <t>
                    It should be noted that the nul character (\u0000) is valid in a JSON string. An
                    instance to validate may contain a string value with this character, regardless
                    of the ability of the underlying programming language to deal with such data.
                </t>
            </section>

            <section title="Validation of numeric instances">
                <t>
                    The JSON specification allows numbers with arbitrary precision, and JSON Schema
                    does not add any such bounds.
                    This means that numeric instances processed by JSON Schema can be arbitrarily large and/or
                    have an arbitrarily long decimal part, regardless of the ability of the
                    underlying programming language to deal with such data.
                </t>
            </section>

            <section title="Regular expressions">
                <t>
                    Two validation keywords, "pattern" and "patternProperties", use regular
                    expressions to express constraints. These regular expressions SHOULD
                    be valid according to the <xref target="ecma262">ECMA 262</xref> regular
                    expression dialect.
                </t>
                <t>
                    Furthermore, given the high disparity in regular expression constructs support,
                    schema authors SHOULD limit themselves to the following regular expression
                    tokens:

                    <list>
                        <t>individual Unicode characters, as defined by the <xref
                        target="RFC7159">JSON specification</xref>;</t>
                        <t>simple character classes ([abc]), range character classes ([a-z]);</t>
                        <t>complemented character classes ([^abc], [^a-z]);</t>
                        <t>simple quantifiers: "+" (one or more), "*" (zero or more), "?" (zero or
                        one), and their lazy versions ("+?", "*?", "??");</t>
                        <t>range quantifiers: "{x}" (exactly x occurrences), "{x,y}" (at least x, at
                        most y, occurrences), {x,} (x occurrences or more), and their lazy
                        versions;</t>
                        <t>the beginning-of-input ("^") and end-of-input ("$") anchors;</t>
                        <t>simple grouping ("(...)") and alternation ("|").</t>
                    </list>
                </t>
                <t>
                    Finally, implementations MUST NOT take regular expressions to be
                    anchored, neither at the beginning nor at the end. This means, for instance,
                    the pattern "es" matches "expression".
                </t>
            </section>

        </section>

        <section title="General validation considerations">

            <section title="Keywords and instance primitive types">
                <t>
                    Most validation keywords only constrain values within a certain primitive type.
                    When the type of the instance is not of the type targeted by the keyword, the
                    validation succeeds.
                </t>
                <t>
                    For example, the "maxLength" keyword will only restrict certain strings (that
                    are too long) from being valid.
                    If the instance is a number, boolean, null, array, or object, the keyword passes
                    validation.
                </t>
            </section>

            <section title="Validation of primitive types and child values">
                <t>
                    Two of the primitive types, array and object, allow for child values.
                    The validation of the primitive type is considered separately from
                    the validation of child instances.
                </t>
                <t>
                    For arrays, primitive type validation consists of validating
                    restrictions on length with "minItems" and "maxItems", while
                    "items" and "additionalItems" determine which subschemas apply
                    to which elements of the array.  In addition, "uniqueItems"
                    and "contains" validate array contents as a whole.
                </t>
                <t>
                    For objects, primitive type validation consists of validating
                    restrictions on which and how many properties appear with
                    "required", "minProperties", "maxProperties", "propertyNames",
                    and the string array form of "dependencies", while "properties",
                    "patternProperties", and "additionalProperties" determine which
                    subschemas apply to which object property values.
                    In addition, the schema form of "dependencies" validates the
                    object as a whole based on the presence of specific property names.
                </t>
            </section>

            <section title="Constraints and missing keywords">
                <t>
                    Each JSON Schema validation keyword adds constraints that
                    an instance must satisfy in order to successfully validate.
                </t>
                <t>
                    Validation keywords that are missing never restrict validation.
                    In some cases, this no-op behavior is identical to a keyword that exists with
                    certain values, and these values are noted where known.
                </t>
            </section>

            <section title="Keyword independence">
                <t>
                    Validation keywords typically operate independently, without
                    affecting each other's outcomes.
                </t>
                <t>
                    For schema author convenience, there are some exceptions:
                    <list>
                        <t>
                            "additionalProperties", whose behavior is defined in terms of
                            "properties" and "patternProperties"; and
                        </t>
                        <t>
                            "additionalItems", whose behavior is defined in terms of "items".
                        </t>
                    </list>
                </t>
            </section>

        </section>

        <section title="Meta-schema">
            <t>
                The current URI for the JSON Schema Validation is
                &lt;http://json-schema.org/draft-06/schema#&gt;.
            </t>
        </section>

        <section title="Validation keywords">
            <t>
                Validation keywords in a schema impose requirements for successful validation of an
                instance.
            </t>

            <section title="Validation keywords for numeric instances (number and integer)">
                <section title="multipleOf">
                    <t>
                        The value of "multipleOf" MUST be a number, strictly greater than 0.
                    </t>
                    <t>
                        A numeric instance is valid only if division by this keyword's value results in
                        an integer.
                    </t>
                </section>

                <section title="maximum">
                    <t>
                        The value of "maximum" MUST be a number, representing an inclusive upper limit
                        for a numeric instance.
                    </t>
                    <t>
                        If the instance is a number, then this keyword validates only if the instance is
                        less than or exactly equal to "maximum".
                    </t>
                </section>

                <section title="exclusiveMaximum">
                    <t>
                        The value of "exclusiveMaximum" MUST be number, representing an exclusive upper
                        limit for a numeric instance.
                    </t>
                    <t>
                        If the instance is a number, then the instance is valid only if it has a value
                        strictly less than (not equal to) "exclusiveMaximum".
                    </t>
                </section>

                <section title="minimum">
                    <t>
                        The value of "minimum" MUST be a number, representing an inclusive lower limit
                        for a numeric instance.
                    </t>
                    <t>
                        If the instance is a number, then this keyword validates only if the instance is
                        greater than or exactly equal to "minimum".
                    </t>
                </section>

                <section title="exclusiveMinimum">
                    <t>
                        The value of "exclusiveMinimum" MUST be number, representing an exclusive lower
                        limit for a numeric instance.
                    </t>
                    <t>
                        If the instance is a number, then the instance is valid only if it has a value
                        strictly greater than (not equal to) "exclusiveMinimum".
                    </t>
                </section>
            </section>

            <section title="Validation keywords for strings">
                <section title="maxLength">
                    <t>
                        The value of this keyword MUST be a non-negative integer.</t>
                    <t>
                        A string instance is valid against this keyword if its
                        length is less than, or equal to, the value of this keyword.
                    </t>
                    <t>
                        The length of a string instance is defined as the number of its
                        characters as defined by <xref target="RFC7159">RFC 7159</xref>.
                    </t>
                </section>

                <section title="minLength">
                    <t>
                        The value of this keyword MUST be a non-negative integer.
                    </t>
                    <t>
                        A string instance is valid against this keyword if its
                        length is greater than, or equal to, the value of this keyword.
                    </t>

                    <t>
                        The length of a string instance is defined as the number of its
                        characters as defined by <xref target="RFC7159">RFC 7159</xref>.
                    </t>
                    <t>
                        Omitting this keyword has the same behavior as a value of 0.
                    </t>
                </section>

                <section title="pattern">
                    <t>
                        The value of this keyword MUST be a string. This string SHOULD be a
                        valid regular expression, according to the ECMA 262 regular expression
                        dialect.
                    </t>
                    <t>
                        A string instance is considered valid if the regular
                        expression matches the instance successfully. Recall: regular
                        expressions are not implicitly anchored.
                    </t>
                </section>
            </section>

            <section title="Validation keywords for arrays">
                <section title="items">
                    <t>
                        The value of "items" MUST be either a valid JSON Schema or an array of valid
                        JSON Schemas.
                    </t>
                    <t>
                        This keyword determines how child instances validate for arrays,
                        and does not directly validate the immediate instance itself.
                    </t>
                    <t>
                        If "items" is a schema, validation succeeds if all elements
                        in the array successfully validate against that schema.
                    </t>
                    <t>
                        If "items" is an array of schemas, validation succeeds if
                        each element of the instance validates against the schema at the
                        same position, if any.
                    </t>
                    <t>
                        Omitting this keyword has the same behavior as an empty schema.
                    </t>
                </section>

                <section title="additionalItems">
                    <t>
                        The value of "additionalItems" MUST be a valid JSON Schema.
                    </t>
                    <t>
                        This keyword determines how child instances validate for arrays,
                        and does not directly validate the immediate instance itself.
                    </t>
                    <t>
                        If "items" is an array of schemas, validation succeeds
                        if every instance element at a position greater than the size
                        of "items" validates against "additionalItems".
                    </t>
                    <t>
                        Otherwise, "additionalItems" MUST be ignored, as the "items"
                        schema (possibly the default value of an empty schema) is
                        applied to all elements.
                    </t>
                    <t>
                        Omitting this keyword has the same behavior as an empty schema.
                    </t>
                </section>

                <section title="maxItems">
                    <t>
                        The value of this keyword MUST be a non-negative integer.
                    </t>
                    <t>
                        An array instance is valid against "maxItems" if its size is
                        less than, or equal to, the value of this keyword.
                    </t>
                </section>

                <section title="minItems">
                    <t>
                        The value of this keyword MUST be a non-negative integer.
                    </t>
                    <t>
                        An array instance is valid against "minItems" if its size is
                        greater than, or equal to, the value of this keyword.
                    </t>
                    <t>
                        Omitting this keyword has the same behavior as a value of 0.
                    </t>
                </section>

                <section title="uniqueItems">
                    <t>
                        The value of this keyword MUST be a boolean.
                    </t>
                    <t>
                        If this keyword has boolean value false, the instance validates
                        successfully. If it has boolean value true, the instance validates
                        successfully if all of its elements are unique.
                    </t>
                    <t>
                        Omitting this keyword has the same behavior as a value of false.
                    </t>
                </section>

                <section title="contains">
                    <t>
                        The value of this keyword MUST be a valid JSON Schema.
                    </t>
                    <t>
                        An array instance is valid against "contains" if at least one of
                        its elements is valid against the given schema.
                    </t>
                </section>
            </section>

            <section title="Validation keywords for objects">
                <section title="maxProperties">
                    <t>
                        The value of this keyword MUST be a non-negative integer.
                    </t>
                    <t>
                        An object instance is valid against "maxProperties" if its
                        number of properties is less than, or equal to, the value of this
                        keyword.
                    </t>
                </section>

                <section title="minProperties">
                    <t>
                        The value of this keyword MUST be a non-negative integer.
                    </t>
                    <t>
                        An object instance is valid against "minProperties" if its
                        number of properties is greater than, or equal to, the value of this
                        keyword.
                    </t>
                    <t>
                        Omitting this keyword has the same behavior as a value of 0.
                    </t>
                </section>

                <section title="required">
                    <t>
                        The value of this keyword MUST be an array.
                        Elements of this array, if any, MUST be strings, and MUST be unique.
                    </t>
                    <t>
                        An object instance is valid against this keyword if every item in the array is
                        the name of a property in the instance.
                    </t>
                    <t>
                        Omitting this keyword has the same behavior as an empty array.
                    </t>
                </section>

                <section title="properties">
                    <t>
                        The value of "properties" MUST be an object.
                        Each value of this object MUST be a valid JSON Schema.
                    </t>
                    <t>
                        This keyword determines how child instances validate for objects,
                        and does not directly validate the immediate instance itself.
                    </t>
                    <t>
                        Validation succeeds if, for each name that appears in both
                        the instance and as a name within this keyword's value, the child
                        instance for that name successfully validates against the
                        corresponding schema.
                    </t>
                    <t>
                        Omitting this keyword has the same behavior as an empty object.
                    </t>
                </section>

                <section title="patternProperties">
                    <t>
                        The value of "patternProperties" MUST be an object. Each property name
                        of this object SHOULD be a valid regular expression, according to the
                        ECMA 262 regular expression dialect. Each property value of this object
                        MUST be a valid JSON Schema.
                    </t>
                    <t>
                        This keyword determines how child instances validate for objects,
                        and does not directly validate the immediate instance itself.
                        Validation of the primitive instance type against this keyword
                        always succeeds.
                    </t>
                    <t>
                        Validation succeeds if, for each instance name that matches any
                        regular expressions that appear as a property name in this keyword's value,
                        the child instance for that name successfully validates against each
                        schema that corresponds to a matching regular expression.
                    </t>
                    <t>
                        Omitting this keyword has the same behavior as an empty object.
                    </t>
                </section>

                <section title="additionalProperties">
                    <t>
                        The value of "additionalProperties" MUST be a valid JSON Schema.
                    </t>
                    <t>
                        This keyword determines how child instances validate for objects,
                        and does not directly validate the immediate instance itself.
                    </t>
                    <t>
                        Validation with "additionalProperties" applies only to the child
                        values of instance names that do not match any names in "properties",
                        and do not match any regular expression in "patternProperties".
                    </t>
                    <t>
                        For all such properties, validation succeeds if the child instance
                        validates against the "additionalProperties" schema.
                    </t>
                    <t>
                        Omitting this keyword has the same behavior as an empty schema.
                    </t>
                </section>

                <section title="dependencies">
                    <t>
                        This keyword specifies rules that are evaluated if the instance is an object and
                        contains a certain property.
                    </t>
                    <t>
                        This keyword's value MUST be an object. Each property specifies a dependency.
                        Each dependency value MUST be an array or a valid JSON Schema.
                    </t>
                    <t>
                        If the dependency value is a subschema, and the dependency key is a property
                        in the instance, the entire instance must validate against the dependency value.
                    </t>
                    <t>
                        If the dependency value is an array, each element in the array,
                        if any, MUST be a string, and MUST be unique. If the dependency key is
                        a property in the instance, each of the items in the dependency
                        value must be a property that exists in the instance.
                    </t>
                    <t>
                        Omitting this keyword has the same behavior as an empty object.
                    </t>
                </section>

                <section title="propertyNames">
                    <t>
                        The value of "propertyNames" MUST be a valid JSON Schema.
                    </t>
                    <t>
                        If the instance is an object, this keyword validates if every property name in
                        the instance validates against the provided schema.
                        Note the property name that the schema is testing will always be a string.
                    </t>
                    <t>
                        Omitting this keyword has the same behavior as an empty schema.
                    </t>
                </section>
            </section>

            <section title="Validation keywords for any instance type">
                <section title="enum">
                    <t>
                        The value of this keyword MUST be an array. This array SHOULD have at
                        least one element. Elements in the array SHOULD be unique.
                    </t>
                    <t>
                        An instance validates successfully against this keyword if its value is
                        equal to one of the elements in this keyword's array value.
                    </t>
                    <t>
                        Elements in the array might be of any value, including null.
                    </t>
                </section>

                <section title="const">
                    <t>
                        The value of this keyword MAY be of any type, including null.
                    </t>
                    <t>
                        An instance validates successfully against this keyword if its value is
                        equal to the value of the keyword.
                    </t>
                </section>

                <section title="type">
                    <t>
                        The value of this keyword MUST be either a string or an array. If it is
                        an array, elements of the array MUST be strings and MUST be unique.
                    </t>
                    <t>
                        String values MUST be one of the six primitive types
                        ("null", "boolean", "object", "array", "number", or "string"),
                        or "integer" which matches any number with a zero fractional part.
                    </t>
                    <t>
                        An instance validates if and only if the instance is in any of the sets listed
                        for this keyword.
                    </t>
                </section>
            </section>

            <section title="Keywords for applying subschemas with boolean logic">
                <section title="allOf">
                    <t>
                        This keyword's value MUST be a non-empty array.
                        Each item of the array MUST be a valid JSON Schema.
                    </t>
                    <t>
                        An instance validates successfully against this keyword if it validates
                        successfully against all schemas defined by this keyword's value.
                    </t>
                </section>

                <section title="anyOf">
                    <t>
                        This keyword's value MUST be a non-empty array.
                        Each item of the array MUST be a valid JSON Schema.
                    </t>
                    <t>
                        An instance validates successfully against this keyword if it validates
                        successfully against at least one schema defined by this keyword's value.
                    </t>
                </section>

                <section title="oneOf">
                    <t>
                        This keyword's value MUST be a non-empty array.
                        Each item of the array MUST be a valid JSON Schema.
                    </t>
                    <t>
                        An instance validates successfully against this keyword if it validates
                        successfully against exactly one schema defined by this keyword's value.
                    </t>
                </section>

                <section title="not">
                    <t>
                        This keyword's value MUST be a valid JSON Schema.
                    </t>
                    <t>
                        An instance is valid against this keyword if it fails to validate
                        successfully against the schema defined by this keyword.
                    </t>
                </section>
            </section>
        </section>

        <section title="Metadata keywords">
            <section title="definitions">
                <t>
                    This keyword's value MUST be an object.
                    Each member value of this object MUST be a valid JSON Schema.
                </t>
                <t>
                    This keyword plays no role in validation per se. Its role is to provide
                    a standardized location for schema authors to inline JSON Schemas into a
                    more general schema.
                </t>

                <t>
                    As an example, here is a schema describing an array of positive
                    integers, where the positive integer constraint is a subschema in
                    "definitions":

                    <figure>
                        <artwork>
<![CDATA[
{
    "type": "array",
    "items": { "$ref": "#/definitions/positiveInteger" },
    "definitions": {
        "positiveInteger": {
            "type": "integer",
            "exclusiveMinimum": 0
        }
    }
}
]]>
                        </artwork>
                    </figure>
                </t>
            </section>

            <section title='"title" and "description"'>
                <t>
                    The value of both of these keywords MUST be a string.
                </t>
                <t>
                    Both of these keywords can be used to decorate a user interface with
                    information about the data produced by this user interface. A title will
                    preferably be short, whereas a description will provide explanation about
                    the purpose of the instance described by this schema.
                </t>
            </section>

            <section title='"default"'>
                <t>
                    There are no restrictions placed on the value of this keyword.
                </t>
                <t>
                    This keyword can be used to supply a default JSON value associated with a
                    particular schema. It is RECOMMENDED that a default value be valid against
                    the associated schema.
                </t>
            </section>

            <section title='"examples"'>
                <t>
                    The value of this keyword MUST be an array.
                    There are no restrictions placed on the values within the array.
                </t>
                <t>
                    This keyword can be used to provide sample JSON values associated with a
                    particular schema, for the purpose of illustrating usage.  It is
                    RECOMMENDED that these values be valid against the associated schema.
                </t>
                <t>
                    Implementations MAY use the value of "default", if present, as
                    an additional example.  If "examples" is absent, "default"
                    MAY still be used in this manner.
                </t>
            </section>

        </section>

        <section title='Semantic validation with "format"'>

            <section title="Foreword">
                <t>
                    Structural validation alone may be insufficient to validate that an instance
                    meets all the requirements of an application. The "format" keyword is defined to
                    allow interoperable semantic validation for a fixed subset of values which are
                    accurately described by authoritative resources, be they RFCs or other external
                    specifications.
                </t>

                <t>
                    The value of this keyword is called a format attribute. It MUST be a string. A
                    format attribute can generally only validate a given set of instance types. If
                    the type of the instance to validate is not in this set, validation for this
                    format attribute and instance SHOULD succeed.
                </t>

            </section>

            <section title="Implementation requirements">
                <t>
                    Implementations MAY support the "format" keyword. Should they choose to do so:

                    <list>
                        <t>they SHOULD implement validation for attributes defined below;</t>
                        <t>they SHOULD offer an option to disable validation for this keyword.</t>
                    </list>

                </t>

                <t>
                    Implementations MAY add custom format attributes. Save for agreement between
                    parties, schema authors SHALL NOT expect a peer implementation to support this
                    keyword and/or custom format attributes.
                </t>
            </section>

            <section title="Defined formats">

                <section title="date-time">
                    <t>
                        This attribute applies to string instances.
                    </t>
                    <t>
                        A string instance is valid against this attribute if it is a valid date
                        representation as defined by <xref target="RFC3339">RFC 3339, section
                        5.6</xref>.
                    </t>
                </section>

                <section title="email">
                    <t>
                        This attribute applies to string instances.
                    </t>
                    <t>
                        A string instance is valid against this attribute if it is a valid
                        Internet email address as defined by <xref target="RFC5322">RFC 5322,
                        section 3.4.1</xref>.
                    </t>
                </section>
                <section title="hostname">
                    <t>
                        This attribute applies to string instances.
                    </t>
                    <t>
                        A string instance is valid against this attribute if it is a valid
                        representation for an Internet host name, as defined by <xref
                        target="RFC1034">RFC 1034, section 3.1</xref>.
                    </t>
                </section>

                <section title="ipv4">
                    <t>
                        This attribute applies to string instances.
                    </t>
                    <t>
                        A string instance is valid against this attribute if it is a valid
                        representation of an IPv4 address according to the "dotted-quad" ABNF
                        syntax as defined in <xref target="RFC2673">RFC 2673, section
                        3.2</xref>.
                    </t>
                </section>

                <section title="ipv6">
                    <t>
                        This attribute applies to string instances.
                    </t>
                    <t>
                        A string instance is valid against this attribute if it is a valid
                        representation of an IPv6 address as defined in <xref
                        target="RFC2373">RFC 2373, section 2.2</xref>.
                    </t>
                </section>

                <section title="uri">
                    <t>
                        This attribute applies to string instances.
                    </t>
                    <t>
                        A string instance is valid against this attribute if it is a valid URI,
                        according to <xref target="RFC3986"/>.
                    </t>
                </section>

                <section title="uri-reference">
                    <t>
                        This attribute applies to string instances.
                    </t>
                    <t>
                        A string instance is valid against this attribute if it is a valid URI
                        Reference (either a URI or a relative-reference),
                        according to <xref target="RFC3986"/>.
                    </t>
                </section>

                <section title="uri-template">
                    <t>
                        This attribute applies to string instances.
                    </t>
                    <t>
                        A string instance is valid against this attribute if it is a valid URI Template
                        (of any level), according to <xref target="RFC6570"/>.
                    </t>
                </section>

                <section title="json-pointer">
                    <t>
                        This attribute applies to string instances.
                    </t>
                    <t>
                        A string instance is valid against this attribute if it
                        is a valid JSON string representation of a JSON Pointer,
                        according to
                        <xref target="RFC6901">RFC 6901, section 5</xref>
                    </t>
                </section>
            </section>
        </section>

        <section title="Security considerations">
            <t>
                JSON Schema validation defines a vocabulary for JSON Schema core and concerns all
                the security considerations listed there.
            </t>
            <t>
                JSON Schema validation allows the use of Regular Expressions, which have numerous
                different (often incompatible) implementations.
                Some implementations allow the embedding of arbitrary code, which is outside the
                scope of JSON Schema and MUST NOT be permitted.
                Regular expressions can often also be crafted to be extremely expensive to compute
                (with so-called "catastrophic backtracking"), resulting in a denial-of-service
                attack.
            </t>
        </section>

        <!--
        <section title="IANA Considerations">
            <t>
                This specification does not have any influence with regards to IANA.
            </t>
        </section>
        -->
    </middle>

    <back>
        <!-- References Section -->
        <references title="Normative References">
            &RFC2119;
            <reference anchor="json-schema">
                <front>
                    <title>JSON Schema: A Media Type for Describing JSON Documents</title>
                    <author/>
                    <date year="2016" month="October"/>
                </front>
                <seriesInfo name="Internet-Draft" value="draft-wright-json-schema-00" />
            </reference>
        </references>

        <references title="Informative References">
            &RFC1034;
            &RFC2373;
            &RFC2673;
            &RFC3339;
            &RFC3986;
            &RFC6570;
            &RFC6901;
            &RFC7159;
            &RFC5322;
            <reference anchor="ecma262"
            target="http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-262.pdf">
                <front>
                    <title>ECMA 262 specification</title>
                    <author/>
                    <date/>
                </front>
            </reference>
        </references>

        <section title="Acknowledgments">
            <t>
                Thanks to
                Gary Court,
                Francis Galiegue,
                Kris Zyp,
                and Geraint Luff
                for their work on the initial drafts of JSON Schema.
            </t>
            <t>
                Thanks to
                Jason Desrosiers,
                Daniel Perrett,
                Erik Wilde,
                Ben Hutton,
                Evgeny Poberezkin,
                Brad Bowman,
                Gowry Sankar,
                Donald Pipowitch,
                and Dave Finlay
                for their submissions and patches to the document.
            </t>
        </section>

        <section title="ChangeLog">
            <t>
                <cref>This section to be removed before leaving Internet-Draft status.</cref>
            </t>
            <t>
                <list style="hanging">
                    <t hangText="draft-wright-json-schema-validation-02">
                        <list style="symbols">
                            <t></t>
                        </list>
                    </t>
                    <t hangText="draft-wright-json-schema-validation-01">
                        <list style="symbols">
                            <t>Standardized on hyphenated format names ("uriref" becomes "uri-ref")</t>
                            <t>Add the formats "uri-template" and "json-pointer"</t>
                            <t>Changed "exclusiveMaximum"/"exclusiveMinimum" from boolean modifiers of "maximum"/"minimum" to independent numeric fields.</t>
                            <t>Split the additionalItems/items into two sections</t>
                            <t>Reworked properties/patternProperties/additionalProperties definition</t>
                            <t>Added "examples" keyword</t>
                            <t>Added "contains" keyword</t>
                            <t>Allow empty "required" and "dependencies" arrays</t>
                            <t>Fixed "type" reference to primitive types</t>
                            <t>Added "const" keyword</t>
                            <t>Added "propertyNames" keyword</t>
                        </list>
                    </t>
                    <t hangText="draft-wright-json-schema-validation-00">
                        <list style="symbols">
                            <t>Added additional security considerations</t>
                            <t>Removed reference to "latest version" meta-schema, use numbered version instead</t>
                            <t>Rephrased many keyword definitions for brevity</t>
                            <t>Added "uriref" format that also allows relative URI references</t>
                        </list>
                    </t>
                    <t hangText="draft-fge-json-schema-validation-01">
                        <list style="symbols">
                            <t>Initial draft.</t>
                            <t>Salvaged from draft v3.</t>
                            <t>Redefine the "required" keyword.</t>
                            <t>Remove "extends", "disallow"</t>
                            <t>Add "anyOf", "allOf", "oneOf", "not", "definitions", "minProperties",
                            "maxProperties".</t>
                            <t>"dependencies" member values can no longer be single strings; at
                            least one element is required in a property dependency array.</t>
                            <t>Rename "divisibleBy" to "multipleOf".</t>
                            <t>"type" arrays can no longer have schemas; remove "any" as a possible
                            value.</t>
                            <t>Rework the "format" section; make support optional.</t>
                            <t>"format": remove attributes "phone", "style", "color"; rename
                            "ip-address" to "ipv4"; add references for all attributes.</t>
                            <t>Provide algorithms to calculate schema(s) for array/object
                            instances.</t>
                            <t>Add interoperability considerations.</t>
                        </list>
                    </t>
                </list>
            </t>
        </section>
    </back>
</rfc>