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127 | 127 |
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128 | 128 | <section title="Overview"> |
129 | 129 | <t> |
130 | | - This document proposes a new media type "application/schema+json" to identify a JSON |
131 | | - Schema for describing JSON data. |
132 | | - It also proposes a further optional media type, "application/schema-instance+json", |
133 | | - to provide additional integration features. |
| 130 | + This document specifies the media type "application/schema+json" which |
| 131 | + can describe a set of JSON documents, classify documents as instances of this set, |
| 132 | + and to generate annotations about a given instance. |
| 133 | + It also specifies "application/schema-instance+json", |
| 134 | + to describe JSON documents known to be instances of a particular schema. |
134 | 135 | JSON Schemas are themselves JSON documents. |
135 | | - This, and related specifications, define keywords allowing authors to describe JSON |
136 | | - data in several ways. |
137 | 136 | </t> |
138 | 137 | <t> |
139 | | - JSON Schema uses keywords to assert constraints on JSON instances or annotate those |
140 | | - instances with additional information. Additional keywords are used to apply |
141 | | - assertions and annotations to more complex JSON data structures, or based on |
142 | | - some sort of condition. |
| 138 | + A JSON Schema document consists of a set of keywords, |
| 139 | + typically encoded as properties in a JSON object. |
| 140 | + The name of the keyword is used as the property name, |
| 141 | + and any arguments to the keyword are provided as the value. |
| 142 | + </t> |
| 143 | + <t> |
| 144 | + Each keyword provides an assertion and/or annotations about the instance. |
| 145 | + Assertions declare constraints placed on potential instances. |
| 146 | + Given a schema and an instance, the schema "accepts" an instance whenever all the assertions accept, |
| 147 | + and the schema "rejects" when any of the assertions reject. |
| 148 | + Schemas may also be used to build a set of JSON documents: |
| 149 | + The "valid set" of a schema consists of all instances that the schema accepts, |
| 150 | + and the "invalid set" of a schema consists of all instances that the schema rejects. |
| 151 | + In a schema without any assertion keywords, the set of all instances is the set of all JSON documents. |
| 152 | + </t> |
| 153 | + <t> |
| 154 | + Schemas may also provide "annotations" to instances: |
| 155 | + metadata that describes the instance. |
| 156 | + For example, you can document the meaning of a property, |
| 157 | + provide localized labels for a property name, |
| 158 | + suggest a default value for new instances, |
| 159 | + generate a list of hyperlinks from the instance, |
| 160 | + or declare relationships between data. |
143 | 161 | </t> |
144 | 162 | <t> |
145 | 163 | To facilitate re-use, keywords can be organized into vocabularies. A vocabulary |
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