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Re: Proposed requirements on solutions that convertXML-illegal

  • From: Timothy Cook <timothywayne.cook@gmail.com>
  • To: "Costello, Roger L." <costello@mitre.org>
  • Date: Tue, 25 Apr 2017 17:03:25 -0300

Re:  Proposed requirements on solutions that convertXML-illegal
I'm not sure I see your problem. If NUL is embeded in a string and your element is defined to contain string content then it works as expected. 

For example nul.xsd is: 

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
 <xs:complexType name="test">
         <xs:element name="key" type="xs:string"></xs:element>
         <xs:element name="message" type="xs:string"></xs:element>
 <xs:element name="testdoc" type="test"></xs:element>  

and nul.xml is:
<?xml version="1.0" encoding="UTF-8"?>
<testdoc   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    <message>Hello \u000C World</message>

Then the nul.xml is perfectly valid.  Below is even a screen shot I took from within Oxygen XML Editor using Xerces as the parser and SaxonEE gives the same result.

On Tue, Apr 25, 2017 at 3:49 PM, Costello, Roger L. <costello@mitre.org> wrote:

Hi Folks,

XML 1.0 has a limited set of characters. Some other data formats have a superset of characters – the other data formats may have characters that would be illegal in XML.

Suppose the other data format is to be converted to XML. How will the illegal characters be handled?

Other data format -> convert -> XML

Example: the JSON data format has a superset of characters. Suppose you want to convert the following JSON to XML:



\u0000 is a JSON encoding of the NUL (hex 0) character. Recall that the NUL character is not allowed in XML.

I am collecting requirements on the process of converting other data formats into XML. Below is my list thus far. Do you agree with the list? Are there requirements that you would add/delete?

1. The conversion must result in legal XML. Thus, conversion of the above JSON must not produce this:


That is not legal (well-formed) XML.

2. The conversion must be round-trippable. The operation must be lossless. Thus, it is not acceptable to convert the above JSON to this:


Data has been lost. That is a lossy operation and is not round-trippable.

3. The conversion must output standard XML. The XML must not contain syntax/encoding that is specific to the other data format. The XML must be processable using standard XML tools. Thus, it is not acceptable to convert the above JSON to this:


That has a JSON-specific encoding embedded within XML. If we wanted, say, to do a string comparison on the value of <key>, the application would need to understand the JSON syntax.

4. The conversion must output readable text. No hexadecimal text output. Thus, it is not acceptable to convert this:

"message": "Hello \u000C World"


to this:




Well, that’s a start. What are the other requirements for converting illegal characters to XML?


Have these requirements boxed me into a situation where no solution is possible?




Timothy Cook

Attachment: nul.png
Description: PNG image

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