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Oxygen XML Editor includes a tool for generating a sample JSON Schema from a JSON file. To generate a sample JSON Schema, select Generate JSON Schema from the Tools > JSON Tools menu. The action opens a dialog box where you can configure a variety of options for generating the JSON Schema file.

Figure 1. Generate JSON Schema Dialog Box
The Generate JSON Schema dialog box includes the following fields and options:
JSON Document URL
The URL of the JSON file. You can specify the path by using the text field, the history drop-down menu, or the browsing actions in the Browse drop-down list.
Output JSON Schema
Path to the folder where the generated JSON Schema will be saved.
Extract matching format for strings
If selected, the generator will try to find a format that matches the string values from the JSON Document.
Add default values for simple types
If selected, the default values (0 for number, "" for string, false for boolean) and examples for string will be added.
Restrict additional content
If selected, additionalProperties (for objects) and additionalItems (for arrays) will be set to false in the resulting schema. By default, these keys are not in the schema, meaning that providing additional content (according to the schema) is allowed.
Open in Editor
If selected, the generated JSON Schema is opened in the editor.

You can click Generate at any point to generate the JSON Schema.