Skip to content

Commit

Permalink
Docs: Improve format documentation (#963)
Browse files Browse the repository at this point in the history 
* fix: remove Format from string.md

* fix: add Format to type.md

* simplify the data and time intro in type.md

* update type.md with new suggestions
  • Loading branch information
@nikhilkalburgi
nikhilkalburgi authored Jan 10, 2025
1 parent 087d54b commit 950e960
Show file tree
Hide file tree
Showing 2 changed files with 61 additions and 126 deletions.
126 changes: 0 additions & 126 deletions pages/understanding-json-schema/reference/string.md
View file
Original file line number Diff line number Diff line change
Expand Up @@ -121,129 +121,3 @@ with an optional area code:
// props { "indent": true, "valid": false }
"(800)FLOWERS"
```

## Format[#format]

The `format` keyword allows for basic semantic identification of certain
kinds of string values that are commonly used. For example, because JSON
doesn\'t have a \"DateTime\" type, dates need to be encoded as strings.
`format` allows the schema author to indicate that the string value
should be interpreted as a date. By default, `format` is just an
annotation and does not effect validation.

Optionally, validator [implementations](../../learn/glossary#implementation) can provide a configuration option
to enable `format` to function as an assertion rather than just an
annotation. That means that validation will fail if, for example, a
value with a `date` format isn\'t in a form that can be parsed as a
date. This can allow values to be constrained beyond what the other
tools in JSON Schema, including [Regular Expressions](../../understanding-json-schema/reference/regular_expressions) can
do.

> Implementations may provide validation for only a subset of the built-in
> formats or do partial validation for a given format. For example, some
> implementations may consider a string an email if it contains a `@`,
> while others might do additional checks for other aspects of a well
> formed email address.
There is a bias toward networking-related formats in the JSON Schema
specification, most likely due to its heritage in web technologies.
However, custom formats may also be used, as long as the parties
exchanging the JSON documents also exchange information about the custom
format types. A JSON Schema validator will ignore any format type that
it does not understand.

### Built-in formats[#built-in-formats]

The following is the list of formats specified in the JSON Schema
specification.

#### Dates and times

Dates and times are represented in [RFC 3339, section 5.6](https://tools.ietf.org/html/rfc3339#section-5.6). This is a subset
of the date format also commonly known as [ISO8601 format](https://www.iso.org/iso-8601-date-and-time-format.html).

- `"date-time"`: Date and time together, for example,
`2018-11-13T20:20:39+00:00`.
- `"time"`: <StarInline label="New in draft 7" /> Time, for example, `20:20:39+00:00`
- `"date"`: <StarInline label="New in draft 7" /> Date, for example, `2018-11-13`.
- `"duration"`: <StarInline label="New in draft 2019-09" /> A duration as defined by the [ISO 8601 ABNF for \"duration\"](https://datatracker.ietf.org/doc/html/rfc3339#appendix-A).
For example, `P3D` expresses a duration of 3 days.

<Keywords label="single: email single: idn-email single: format; email single: format; idn-email" />

#### Email addresses

- `"email"`: Internet email address, see [RFC 5321, section 4.1.2](http://tools.ietf.org/html/rfc5321#section-4.1.2).
- `"idn-email"`: <StarInline label="New in draft 7" /> The internationalized form of an Internet email
address, see [RFC 6531](https://tools.ietf.org/html/rfc6531).

<Keywords label="single: hostname single: idn-hostname single: format; hostname single: format; idn-hostname" />

#### Hostnames

- `"hostname"`: Internet host name, see [RFC 1123, section 2.1](https://datatracker.ietf.org/doc/html/rfc1123#section-2.1).
- `"idn-hostname"`: <StarInline label="New in draft 7" /> An internationalized Internet host name, see
[RFC5890, section 2.3.2.3](https://tools.ietf.org/html/rfc5890#section-2.3.2.3).

<Keywords label="single: ipv4 single: ipv6 single: format; ipv4 single: format; ipv6" />

#### IP Addresses

- `"ipv4"`: IPv4 address, according to dotted-quad ABNF syntax as
defined in [RFC 2673, section 3.2](http://tools.ietf.org/html/rfc2673#section-3.2).
- `"ipv6"`: IPv6 address, as defined in [RFC 2373, section 2.2](http://tools.ietf.org/html/rfc2373#section-2.2).

<Keywords label="single: uuid single: uri single: uri-reference single: iri single: iri-reference single: format; uuid single: format; uri single: format; uri-reference single: format; iri single: format; iri-reference" />

#### Resource identifiers

- `"uuid"`: <StarInline label="New in draft 2019-09" /> A Universally Unique Identifier as defined by [RFC 4122](https://datatracker.ietf.org/doc/html/rfc4122). Example:
`3e4666bf-d5e5-4aa7-b8ce-cefe41c7568a`
- `"uri"`: A universal resource identifier (URI), according to
[RFC3986](http://tools.ietf.org/html/rfc3986).
- `"uri-reference"`: <StarInline label="New in draft 6" /> A URI Reference (either a URI or a
relative-reference), according to [RFC3986, section 4.1](http://tools.ietf.org/html/rfc3986#section-4.1).
- `"iri"`: <StarInline label="New in draft 7" /> The internationalized equivalent of a \"uri\", according to
[RFC3987](https://tools.ietf.org/html/rfc3987).
- `"iri-reference"`: <StarInline label="New in draft 7" /> The internationalized equivalent of a
\"uri-reference\", according to
[RFC3987](https://tools.ietf.org/html/rfc3987)

If the values in the schema have the ability to be relative to a
particular source path (such as a link from a webpage), it is generally
better practice to use `"uri-reference"` (or `"iri-reference"`) rather
than `"uri"` (or `"iri"`). `"uri"` should only be used when the path
must be absolute.

<Keywords label="single: uri-template single: format; uri-template" />

#### URI template

- `"uri-template"`: <StarInline label="New in draft 6" /> A URI Template (of any level) according to
[RFC6570](https://tools.ietf.org/html/rfc6570). If you don\'t
already know what a URI Template is, you probably don\'t need this
value.

<Keywords label="single: json-pointer single: relative-json-pointer single: format; json-pointer single: format; relative-json-pointer" />

#### JSON Pointer

- `"json-pointer"`: <StarInline label="New in draft 6" /> A JSON Pointer, according to
[RFC6901](https://tools.ietf.org/html/rfc6901). There is more
discussion on the use of JSON Pointer within JSON Schema in
[Structuring a complex schema](../../understanding-json-schema/structuring). Note that this should be used only when
the entire string contains only JSON Pointer content, e.g.
`/foo/bar`. JSON Pointer URI fragments, e.g. `#/foo/bar/` should use
`"uri-reference"`.
- `"relative-json-pointer"`: <StarInline label="New in draft 7" /> A [relative JSON pointer](https://tools.ietf.org/html/draft-handrews-relative-json-pointer-01).

<Keywords label="single: regex single: format; regex" />

#### Regular Expressions

- `"regex"`: <StarInline label="New in draft 7" /> A regular expression, which should be valid according to
the [ECMA 262](https://www.ecma-international.org/publications-and-standards/standards/ecma-262/)
[dialect](../../learn/glossary#dialect).

Be careful, in practice, JSON schema validators are only required to
accept the safe subset of [regular expressions](../../understanding-json-schema/reference/regular_expressions) described elsewhere in this document.
61 changes: 61 additions & 0 deletions pages/understanding-json-schema/reference/type.md
View file
Original file line number Diff line number Diff line change
Expand Up @@ -181,3 +181,64 @@ types. For example, numeric types have a way of specifying a numeric
range, that would not be applicable to other types. In this reference,
these validation keywords are described along with each of their
corresponding types in the following chapters.

## Format[#format]

The `format` keyword conveys semantic information for values that may be difficult or impossible to describe using JSON Schema. Typically, this semantic information is described by other documents. The JSON Schema Validation specification defines several formats, but this keyword also allows schema authors to define their own formats.

For example, because JSON doesn't have a "DateTime" type, dates need to be encoded as strings. `format` allows the schema author to indicate that the string value should be interpreted as a date. By default, `format` is just an annotation and does not affect validation.

Optionally, validator [implementations](../../learn/glossary#implementation) can provide a configuration option to enable `format` to function as an assertion rather than just an annotation. That means that validation fails when, for example, a value with a `date` format isn't in a form that can be parsed as a date. This allows values to be constrained beyond what other tools in JSON Schema, including [Regular Expressions](../../understanding-json-schema/reference/regular_expressions), can do.

> Implementations may provide validation for only a subset of the built-in formats or do partial validation for a given format. For example, some implementations may consider a string an email if it contains an `@`, while others might perform additional checks for other aspects of a well-formed email address.
The JSON Schema specification has a bias toward networking-related formats due to its roots in web technologies. However, custom formats may also be used if the parties exchanging the JSON documents share information about the custom format types. A JSON Schema validator will ignore any format type it does not understand.

### Built-in Formats

It should be noted that `format` is not limited to a specific set of valid values or types. Users may define their own custom keywords including ones that work with JSON data types other than `string`, such as `number`. Below, we cover the formats specified in the JSON Schema specification.

#### Dates and Times

Dates and times are represented in [RFC 3339, section 5.6](https://tools.ietf.org/html/rfc3339#section-5.6). RFC 3339 is a specification from the Internet Engineering Task Force (IETF).

- `"date-time"`: Date and time together, for example, `2018-11-13T20:20:39+00:00`.
- `"time"`: <StarInline label="New in draft 7" /> Time, for example, `20:20:39+00:00`.
- `"date"`: <StarInline label="New in draft 7" /> Date, for example, `2018-11-13`.
- `"duration"`: <StarInline label="New in draft 2019-09" /> A duration as defined by the [ISO 8601 ABNF for "duration"](https://datatracker.ietf.org/doc/html/rfc3339#appendix-A). For example, `P3D` expresses a duration of 3 days.

#### Email Addresses

- `"email"`: Internet email address, see [RFC 5321, section 4.1.2](http://tools.ietf.org/html/rfc5321#section-4.1.2).
- `"idn-email"`: <StarInline label="New in draft 7" /> The internationalized form of an Internet email address, see [RFC 6531](https://tools.ietf.org/html/rfc6531).

#### Hostnames

- `"hostname"`: Internet host name, see [RFC 1123, section 2.1](https://datatracker.ietf.org/doc/html/rfc1123#section-2.1).
- `"idn-hostname"`: <StarInline label="New in draft 7" /> An internationalized Internet host name, see [RFC5890, section 2.3.2.3](https://tools.ietf.org/html/rfc5890#section-2.3.2.3).

#### IP Addresses

- `"ipv4"`: IPv4 address, according to dotted-quad ABNF syntax as defined in [RFC 2673, section 3.2](http://tools.ietf.org/html/rfc2673#section-3.2).
- `"ipv6"`: IPv6 address, as defined in [RFC 2373, section 2.2](http://tools.ietf.org/html/rfc2373#section-2.2).

#### Resource Identifiers

- `"uuid"`: <StarInline label="New in draft 2019-09" /> A Universally Unique Identifier as defined by [RFC 4122](https://datatracker.ietf.org/doc/html/rfc4122). Example: `3e4666bf-d5e5-4aa7-b8ce-cefe41c7568a`.
- `"uri"`: A universal resource identifier (URI), according to [RFC3986](http://tools.ietf.org/html/rfc3986).
- `"uri-reference"`: <StarInline label="New in draft 6" /> A URI Reference (either a URI or a relative-reference), according to [RFC3986, section 4.1](http://tools.ietf.org/html/rfc3986#section-4.1).
- `"iri"`: <StarInline label="New in draft 7" /> The internationalized equivalent of a "uri", according to [RFC3987](https://tools.ietf.org/html/rfc3987).
- `"iri-reference"`: <StarInline label="New in draft 7" /> The internationalized equivalent of a "uri-reference", according to [RFC3987](https://tools.ietf.org/html/rfc3987).

#### URI Template

- `"uri-template"`: <StarInline label="New in draft 6" /> A URI Template (of any level) according to [RFC6570](https://tools.ietf.org/html/rfc6570). If you don\'t already know what a URI Template is, you probably don\'t need this value.

#### JSON Pointer

- `"json-pointer"`: <StarInline label="New in draft 6" /> A JSON Pointer, according to [RFC6901](https://tools.ietf.org/html/rfc6901). There is more discussion on using JSON Pointer within JSON Schema in [Structuring a complex schema](../../understanding-json-schema/structuring). Note that this should be used only when the entire string contains only JSON Pointer content, e.g., `/foo/bar`. JSON Pointer URI fragments, e.g., `#/foo/bar/` should use `"uri-reference"`.
- `"relative-json-pointer"`: <StarInline label="New in draft 7" /> A [relative JSON pointer](https://tools.ietf.org/html/draft-handrews-relative-json-pointer-01).

#### Regular Expressions

- `"regex"`: <StarInline label="New in draft 7" /> A regular expression that should be valid according to the [ECMA 262](https://www.ecma-international.org/publications-and-standards/standards/ecma-262/) [dialect](../../learn/glossary#dialect). Be careful, in practice, JSON Schema validators are only required to accept the safe subset of [regular expressions](../../understanding-json-schema/reference/regular_expressions) described elsewhere in this document.

0 comments on commit 950e960

Please sign in to comment.