Represent space and tab in XML tag

Question

How to represent space and tab in XML tag. Is there any special characters for them to represent.

Answer 1

^{New, expanded answer to an old, commonly asked question...}

Whitespace in XML Component Names

Summary: Whitespace characters are not permitted in XML element or attribute names.

Here are the main Unicode code points related to whitespace:

• #x0009 CHARACTER TABULATION
• #x0020 SPACE
• #x000A LINE FEED (LF)
• #x000D CARRIAGE RETURN (CR)
• #x00A0 NO-BREAK SPACE
• [#x2002-#x200A] EN SPACE through HAIR SPACE
• #x205F MEDIUM MATHEMATICAL SPACE
• #x3000 IDEOGRAPHIC SPACE

None of these code points are permitted by the W3C XML BNF for XML names:

NameStartChar ::= ":" | [A-Z] | "_" | [a-z] | [#xC0-#xD6] | [#xD8-#xF6] |
                  [#xF8-#x2FF] | [#x370-#x37D] | [#x37F-#x1FFF] |
                  [#x200C-#x200D] | [#x2070-#x218F] | [#x2C00-#x2FEF] |
                  [#x3001-#xD7FF] | [#xF900-#xFDCF] | [#xFDF0-#xFFFD] |
                  [#x10000-#xEFFFF]
NameChar      ::= NameStartChar | "-" | "." | [0-9] | #xB7 | [#x0300-#x036F] |
                  [#x203F-#x2040]
Name          ::= NameStartChar (NameChar)*

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Whitespace in XML Content (Not Component Names)

Summary: Whitespace characters are, of course, permitted in XML content.

All of the above whitespace codepoints are permitted in XML content by the W3C XML BNF for Char:

Char ::= #x9 | #xA | #xD | [#x20-#xD7FF] | [#xE000-#xFFFD] | [#x10000-#x10FFFF]
/* any Unicode character, excluding the surrogate blocks, FFFE, and FFFF. */

Unicode code points can be inserted as character references. Both decimal &#decimal; and hexadecimal &#xhex; forms are supported.

• Hexadecimal  Decimal  Unicode Name
•    or         CHARACTER TABULATION
•    or         LINE FEED (LF)
•    or         CARRIAGE RETURN (CR)
•    or         SPACE
•     or       NO-BREAK SPACE