Re: [xml-dev] RE: How to represent mixed content in JSON and JSON Schema

[David Carlisle <d.p.carlisle@gmail.com>]

On 16 July 2018 at 19:56, Costello, Roger L. <costello@mitre.org> wrote:
> Hi Folks,
>
>
>
> I have examined several approaches that people have developed to represent
> mixed content in JSON. I have identified their best features.
>
>
>
> I created an approach that incorporates all their best features.
>
>
>
> Below is my recommended approach for representing mixed content in JSON. I
> welcome your comments and critiques.
>
>
>
> I will illustrate my approach by showing how to convert the following XML
> containing mixed content to JSON:
>
>
>
> <example>Some text <bdo dir="rtl">reverse this text <bdo dir="ltr">not this
> text</bdo></bdo> finishing text</example>
>
>
>
> Rule #1: Represent each XML element as a JSON object property, where the
> property name is the element name.
>
>
>
> The <example> element is represented as this JSON object property:
>
>
>
> "example": …
>
>
>
> Rule #2: Represent each XML text node as a JSON object property, where the
> property name is $ and the property value is a string corresponding to the
> string value of the text node.
>
>
>
> The text node within this <bdo> element:
>
>
>
> <bdo dir="ltr">not this text</bdo>
>
>
>
> is represented by this JSON property/value pair:
>
>
>
> "$": "not this text"
>
>
>
> Rule #3: Represent each XML attribute/value pair as a JSON object
> property/value pair, where the property name is the attribute name preceded
> by the @ symbol and the property value is a string corresponding to the
> string value of the attribute value.
>
>
>
> The dir=”ltr” within this <bdo> element:
>
>
>
> <bdo dir="ltr">not this text</bdo>
>
>
>
> is represented by this JSON property/value pair:
>
>
>
> "@dir": "ltr"
>
>
>
> Rule #4: If an element’s content is not mixed (mixed=”false”), then
> represent its content as a JSON object:
>
>
>
> The following <bdo> element does not have mixed content:
>
>
>
> <bdo dir="ltr">not this text</bdo>
>
>
>
> Applying Rules 1-4 yields this JSON:
>
>
>
> "bdo": {
>                 "@dir": "ltr",
>                 "$": "not this text"
>            }
>
>
>
> Rule #5: If an element has mixed content, then represent the element’s
> content (including attribute/value pairs) in JSON as an array, where each
> item is embedded in a JSON object. The attributes must be the first items in
> the array. The remaining JSON array items must be in the same order as they
> are in the XML mixed content.
>
>
>
> Per Rule #3 attribute/value pairs are represented as JSON object
> property/value pairs. Per this rule, embed each property/value pair within a
> JSON object.
> Per Rule #2 text nodes are represented as JSON object property/value pairs.
> Per this rule, embed each property/value pair within a JSON object.
> Per Rule #1 elements are represented as JSON object property/value pairs.
> Per this rule, embed each property/value pair within a JSON object.
>
>
>
> The outer <bdo> element has mixed content:
>
>
>
> <bdo dir="rtl">reverse this text <bdo dir="ltr">not this text</bdo></bdo>
>
>
>
> Represent it in JSON this way:
>
>
>
> "bdo": [
>                {"@dir": "rtl"},
>                {"$": "reverse this text"},
>                {"bdo": {
>                                  "@dir": "ltr",
>                                  "$": "not this text"
>                             }
>                },
>               {"$": "finishing text"}
>           ]
>
>
>
> Rule #6: If an element is the root element, embed it in a JSON object.
>
>
>
> The <example> element is the root element, so it is embedded in a JSON
> object:
>
>
>
> {"example": [
>     {"$": "some text "},
>     {"bdo": [
>         {"@dir": "rtl"},
>         {"$": "reverse this text"},
>         {"bdo": {
>             "@dir": "ltr",
>             "$": "not this text"
>           }
>         },
>         {"$": "finishing text"}
>       ]
>     }
>   ]
> }
>
>
>
> Read as: This JSON represents an <example> element which has mixed content.
> The mixed content contains text (some text), followed by a <bdo> element,
> followed by text (finishing text). The outer <bdo> element contains mixed
> content and an attribute dir with value rtl. Its mixed content is text
> (reverse this text) followed by an inner <bdo> element. The inner <bdo>
> element contains text (not this text) and an attribute dir with value ltr.
>
>
>
> Comments?


seems somewhat underspecified:-)

you seem to be using "does not have mixed content" to mean "has a
single child, which is text"  but mixed content usually means has a
mix of text and element nodes, so an element with just element
children is not considered mxed content. but also

<foo>  x<!--abc-->y</foo>

is this represented as having a single text node, or two?

<foo xmlns="">x</x</foo>

is this represented as having 1 attribute or none?

is <foo><![CDATA[x]]></foo> represented the same way as <foo>x</foo>

is
<foo>
 <x/>
 <y/>
</foo>
represented the same way as
<foo><x/><y/></foo>

is
<foo>&#65;</foo> the same as <foo>A</foo>

David



>
>
>
> /Roger