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Re: The most common syntax errors people make when creatingXML

• From: Michael Kay <mike@saxonica.com>
• To: Roger L Costello <costello@mitre.org>
• Date: Sun, 15 May 2022 23:57:05 +0100

Those are errors that people make when creating XML by hand using a text editor that doesn't understand XML. I wouldn't have thought many people do that.

Judging from StackOverflow, by far the most common error encountered in generated XML is a failure to escape special characters (`&`, and `<`; and `"` within attribute values). I guess programs that generate XML also have bugs like mismatched end tags or missing whitespace between attributes, but those errors don't get past internal testing so production parsers don't need to deal with them. These bugs will tend to make all generated XML output invalid, which will soon be fixed, whereas a failure to escape special characters won't be caught in testing unless someone generates test data containing these characters, which means the bug will make it into production software.

In hand-generated XML, I would rate unintended self-closing tags quite high: <x att="1"/>content</x>.

Michael Kay
Saxonica

> On 15 May 2022, at 23:16, Roger L Costello <costello@mitre.org> wrote:
> 
> Hi Folks,
> 
> I am creating (for fun) an XML parser. I'd like my parser to detect and fix the most common syntax errors in XML documents. 
> 
> I created a list of errors that I commonly make. See below. What errors do you find yourself commonly making? I would appreciate it if you would add to the list.  
> 
> Common syntax errors in XML documents:
> 
> 1. Two quotes at the end of a namespace declaration. Example:
> 
> xmlns:fn="http://www.w3.org/2005/xpath-functions""
> 
> 2. End tag repeated. Example:
> 
> </xsl:stylesheet>
> 
> 
> </xsl:stylesheet>
> 
> 3. Missing space after attribute value delimiter. Example:
> 
> <Document id="ab3"reviewer="John Doe">
> 
> 4. Incorrect syntax for start of a CDATA section. Example:
> 
> <[CDATA[            it should be <![CDATA[
> 
> 5. Incorrect syntax for the end of a CDATA section. Example:
> 
> ]>                          it should be ]]>
> 
> 6. Missing slash in end tag. Example:
> 
> <Author>John Doe<Author>
> 
> 7. Missing question mark at end of XML declaration. Example:
> 
> <?xml version="1.0">
> 
> 8. Unescaped ampersand. Example:
> 
> <Publisher>Harper & Row</Publisher>
> 
> 9. Missing semicolon at end of entity. Example:
> 
> <Publisher>Harper &amp Row</Publisher>
> 
> 10. Space in tag name. Example:
> 
> <New York>
> 
> What else?
> 
> /Roger
> 
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• References:
  • The most common syntax errors people make when creating XMLdocuments?
    • From: Roger L Costello <costello@mitre.org>