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doc/schema.md

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 RapidJSON implemented a JSON Schema validator for [JSON Schema Draft v4](http://json-schema.org/documentation.html). If you do not familiar with JSON Schema, you may refer to [Understanding JSON Schema](http://spacetelescope.github.io/understanding-json-schema/).
 
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 ## Basic Usage
 
 First of all, you need to parse a JSON Schema into `Document`, and then compile the `Document` into `SchemaDocument`.