CBOR typeof tag

Specifies a CBOR tag applied to any CBOR item for describing it's type.

Overview

This document specifies a CBOR tag 15 applied to any CBOR item for describing it's type:

Tag: 15
Data item: any
Semantics: Describes the type of the data item
Point of contact: Yan Qing <txr1883@gmail.com>
Description of semantics: https://github.com/cbor-schema/cbor-typeof-tag

This tag is used to express CBOR data structures (also known as CBOR Schema) in CBOR.

Basic Type Examples

Typeof Unsigned Integer

An example of expressing unsigned integer with default value 0:

0xcf00    -- Diagnostic: 15(0), alias typeof(0)
CF        -- Tag 15
   00     -- 0

Valid CBOR items: 0, 1, 2, ...

Invalid CBOR items: -1, "abc", null, ...

Typeof Negative Integer

An example of expressing negative integer with default value -1:

0xcf20    -- Diagnostic: 15(-1), alias typeof(-1)
CF        -- Tag 15
   20     -- -1

Valid CBOR items: -1, -2, -3, ...

Invalid CBOR items: 0, "abc", null, ...

Typeof Byte String

An example of expressing byte string with default zero bytes:

0xcf40    -- Diagnostic: 15(h''), alias typeof(h'')
CF        -- Tag 15
   40     -- h''

Valid CBOR items: h'', h'01020304', ...

Invalid CBOR items: 0, "abc", null, ...

Typeof Text String

An example of expressing text string with default empty text:

0xcf60    -- Diagnostic: 15(""), alias typeof("")
CF        -- Tag 15
   60     -- ""

Valid CBOR items: "", "abc", ...

Invalid CBOR items: 0, h'', null, ...

Typeof Array

An example of expressing array with any type of items:

0xcf80    -- Diagnostic: 15([]), alias typeof([])
CF        -- Tag 15
   80     -- []

Valid CBOR items: [], [1, 2], [1, "abc", null], ...

Invalid CBOR items: 0, {}, null, ...

An example of expressing array with unsigned integer items:

0xcf81cf00    -- Diagnostic: 15([15(0)])
CF            -- Tag 15
   81         -- Array of length 1
      CF00    -- 15(0)

Valid CBOR items: [], [1], [1, 2], ...

Invalid CBOR items: 0, {}, null, [-1], ...

Typeof Tuples

An example of expressing a two-tuple:

0xcf82cf00cf00    -- Diagnostic: 15([15(0), 15(0)])
CF                -- Tag 15
   82             -- Array of length 2
      CF00        -- 15(0)
      CF00        -- 15(0)

Valid CBOR items: [0, 0], [1, 2], [1, 99], ...

Invalid CBOR items: [0], [0, 1, 2], [0, ""], {}, null, ...

An example of expressing a triple:

0xcf83cf60cf00cf80    -- Diagnostic: 15([15(""), 15(0), 15([])])
CF                      -- Tag 15
   83                   -- Array of length 3
      CF60              -- 15("")
      CF00              -- 15(0)
      CF80              -- 15([])

Valid CBOR items: ["", 0, []], ["key", 1, [1, 2]], ...

Invalid CBOR items: [0], [0, 1, 2], ["", 0, null], {}, null, ...

Typeof Object

An example of expressing object with any type of keys and values:

0xcfa0    -- Diagnostic: 15({})
CF        -- Tag 15
   A0     -- []

Valid CBOR items: {}, {1: 2, 3: 4}, {"a": 1, "b": [2, 3]}, ...

Invalid CBOR items: 0, [], null, ...

An example of expressing object with text string keys and unsigned integer values:

0xcfa1cf60cf00    -- Diagnostic: 15({15(""): 15(0)})
CF                -- Tag 15
   A1             -- Map of 1 key/value pair
      CF60        -- 15(""), typeof key
      CF00        -- 15(0), typeof value

Valid CBOR items: {}, {"key1": 1}, {"key": 1, "key2": 1}, ...

Invalid CBOR items: 0, {1: 2, 3: 4}, null, [], ...

An example of expressing object with specified keys and values:

0xcfa26161cf006162cf60    -- Diagnostic: 15({"a": 15(0), "b": 15("")})
CF                    -- Tag 15
   A2                 -- Map of 2 key/value pair
      6161            -- "a", specified key
         CF00         -- 15(0), typeof value
      6162            -- "b", specified key
         CF60         -- 15(""), typeof value

Valid CBOR items: {"a": 1, "b": ""}, {"a": 1, "b": "abc"}, ...

Invalid CBOR items: {}, {"a": 1, 3: 4}, null, [], ...

Typeof null

An example of expressing type of null:

0xcff6    -- Diagnostic: 15(null)
CF        -- Tag 15
   F6     -- null

Valid CBOR items: null

Invalid CBOR items: -1, "abc", undefined, ...

Typeof undefined

An example of expressing type of undefined:

0xcff7    -- Diagnostic: 15(undefined)
CF        -- Tag 15
   F7     -- undefined

Valid CBOR items: undefined

Invalid CBOR items: -1, "abc", null, ...

Typeof Boolean

An example of expressing type of boolean with default value false::

0xcff4    -- Diagnostic: 15(false)
CF        -- Tag 15
   F4     -- false

Valid CBOR items: false, true

Invalid CBOR items: -1, "abc", null, ...

An example of expressing type of boolean with default value true::

0xcff5    -- Diagnostic: 15(true)
CF        -- Tag 15
   F5     -- true

Valid CBOR items: false, true

Invalid CBOR items: -1, "abc", null, ...

Union Types Examples

We use Tag 15 with Indefinite-length array to express union types.

Typeof Integer

An example of expressing integer with default value 0:

0xcf90cf00cf20ff    -- Diagnostic: 15([_ 15(0), 15(-1)])
CF                  -- Tag 15
   90               -- Start indefinite-length array
      CF00          -- 15(0), unsigned integer
      CF20          -- 15(-1), or negative integer
      FF            -- Break (end of array)

Valid CBOR items: 0, 1, -1, ...

Invalid CBOR items: true, "abc", null, ...

Typeof Object and null

An example of expressing object with specified keys and values:

cfa2646e616d65cf6063616765cf90cf00cff6ff    -- Diagnostic: 15({"name": 15(""), "age": 15([_ 15(0), 15(null)])})
CF                                          -- Tag 15
   A2                                       -- Map of 2 key/value pair
      646E616D65                            -- "name", specified key
         CF60                               -- 15(""), text string value
      63616765                              -- "age", specified key
         CF90CF00CFF6FF                     -- 15([_ 15(0), 15(null)]), unsigned integer value or null

Valid CBOR items: {"name": "alice", "age": 18}, {"name": "alice", "age": null}, ...

Invalid CBOR items: {}, {"name": "alice", "age": -1}, {"name": "alice"}, {"name": "alice", "age": 18, "address": {}}, ...

Typeof Object and undefined

An example of expressing object with specified keys and values:

cfa2646e616d65cf6063616765cf90cf00cff7ff    -- Diagnostic: 15({"name": 15(""), "age": 15([_ 15(0), 15(undefined)])})
CF                                          -- Tag 15
   A2                                       -- Map of 2 key/value pair
      646E616D65                            -- "name", specified key
         CF60                               -- 15(""), text string value
      63616765                              -- "age", specified key
         CF90CF00CFF7FF                     -- 15([_ 15(0), 15(undefined)]), unsigned integer value or not exists (undefined)

Valid CBOR items: {"name": "alice", "age": 18}, {"name": "alice"}, ...

Invalid CBOR items: {}, {"name": "alice", "age": -1}, {"name": "alice", "age": null}, {"name": "alice", "age": 18, "address": {}}, ...

Tuple or Triple

An example of expressing a tuple or triple:

0xcf83cf60cf00cf90cf80cff7ff    -- Diagnostic: 15([15(0), 15(""), 15([_ 15([]), 15(undefined)])])
CF                      -- Tag 15
   83                   -- Array of length 3
      CF60              -- 15("")
      CF00              -- 15(0)
      CF90CF80CFF7FF    -- 15([])

Valid CBOR items: ["", 0], ["", 0, []], ["key", 1, [1, 2]], ...

Invalid CBOR items: [0], [0, 1, 2], ["", 0, null], {}, null, ...

Type Annotation Examples

We use Tag 15 with Indefinite-length array and a Indefinite-length map value to express type with annotation.

Typeof Unsigned Integer with Type Annotation

An example of expressing unsigned integer with default value 0, max value 100 and min value 0:

0xcf90cf00bf636d696e00636d61781864ffff    -- Diagnostic: 15([_ 15(0), {_ "min": 0, "max": 100}])
CF                  -- Tag 15
   90               -- Start indefinite-length array
      CF00          -- 15(0), unsigned integer
      BF            -- Start indefinite-length map
         636d696e   -- "min", specified key
            00      -- 0, value
         636d6178   -- "max", specified key
            1864    -- 100, value
         FF         -- Break (end of map)
      FF            -- Break (end of array)

Valid CBOR items: 0, 1, 2, ..., 100

Invalid CBOR items: -1, 101, null, ...

The annotation vocabularies can include "enum", "min", "max", and "comment" among others. These will be defined in the CBOR Schema.