RE: [xml-dev] Your XML documents may use different sets of characters, d

["Costello, Roger L." <costello@mitre.org>]

Hi Folks,

Excellent feedback!  Thanks!

Here's a summary of what I've learned. Please tell me where I err.

The following statements apply to "data" not to "markup" (i.e., element names, attribute names).

1. Except for unpaired surrogate codepoints and a few control characters, you can use any character you want in XML documents.

2. The characters don't have to be defined in the Unicode specification.

3. For characters that don't have a visual representation or aren't in the Unicode character set, you can use them  via XML's character entity mechanism, e.g., ￭

4. Implementers of XML applications are free to choose which version of Unicode they will support. Thus, one implementer of an XML Schema validator may choose to support Unicode 2.0, while another implementer of an XML Schema validator may choose to support Unicode 2.1. One implementer of an XSLT processor may choose to support Unicode 2.0, while another implementer of an XSLT processor may choose to support Unicode 2.1.

5. In XML applications that use regular expressions (e.g. XML Schema, XSLT), be careful about using regexes that contain regex categories such as Nd. The characters in those regex categories may vary depending on which version of Unicode an implementer supports. Thus, your application may execute without errors with one vendor's tool and fail on another.

6. CREPDL is a technology that allows you to precisely define the universe of characters that you want to allow in your XML documents.

/Roger