What is the standard to map JSON values to XML elements?

There seems to be no industry standard on how to map JSON values to XML elements.

But there are some commonly used conventions:

1. Automatically adding a root element with "root" or "document" as the element tag. For example:

JSON: 
{
    "a": 1,
    "b": 2
}

XML:
<root>
  <a>1</a>
  <b>2</b>
</root>

2. JSON String and Boolean values are converted to XML text content as is. For example:

JSON: 
{
    "a": "20.20",
    "b": true
}

XML:
<root>
  <a>20.20</a>
  <b>true</b>
</root>

3. JSON Number values are normalized first and then converted to XML text contents. For example:

JSON: 
{
    "a": 20.0200,
    "b": 0.314159e01
}

XML:
<root>
  <a>20.02</a>
  <b>3.14159</b>
</root>

4. JSON Null values are converted to empty XML text contents. For example:

JSON: 
{
    "a": null
}

XML:
<root>
  <a/>
</root>

5. JSON Array values are converted to a sequence of XML sub elements with "element" at the tag. For example:

JSON: 
[
    2,
    4,
    8
]

XML:
<root>
  <element>2</element>
  <element>4</element>
  <element>8</element>
</root>

6. JSON Object values are converted to a sequence of XML sub elements with their property names as element tags. Any illegal characters in XML tag names are placed with "_". XML tag names will be prefixed with "_" if they start with numeric characters. For example:

JSON: 
{
    "a": null,
    "x+y": "X plus Y",
    "x-y": "X minus Y",
    "007": "Double O Seven",
    "fyi.pi": 0.314159e01,
    "fyi:pi": 0.314159e01,
    "fyi_pi": "0.314159e01",
    "fyi>pi": "31.4159e-1",
    "error msg": "Something wrong!"
}

XML:
<root>
  <a/>
  <x_y>X plus Y</x_y>
  <x-y>X minus Y</x-y>
  <_007>Double O Seven</_007>
  <fyi.pi>3.14159</fyi.pi>
  <fyi_pi>3.14159</fyi_pi>
  <fyi_pi>0.314159e01</fyi_pi>
  <fyi_pi>31.4159e-1</fyi_pi>
  <error_msg>Something wrong!</error_msg>
</root>

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