What are the rules for a well-formed XML document?
A well-formed XML document must have a single root element, such as
that contains all other elements. 2. Tags must be nested and closed correctly and cannot overlap. For example, text
is correct. 3. Tag names are case-sensitive, and the opening and closing tags must match exactly. 4. The attribute value must be enclosed in quotation marks, such as src="photo.jpg". 5. Attribute names within elements cannot be repeated, such as id cannot appear twice. 6. Special characters such as , & need to be escaped into , & or wrapped with CDATA. 7. Unescaped symbols such as or . XML that conforms to these rules can be parsed correctly, and validity requires additional schema definitions such as DTD or XSD.
A well-formed XML document follows strict syntactic rules defined by the W3C to ensure it can be properly parsed and processed. Unlike HTML, XML does not have predefined tags, so correctness depends entirely on structure and syntax. Here are the essential rules:
1.Single Root Element
A well-formed XML document must have exactly one root element that contains all other elements.
Example:2. Properly Nested and Closed Tags
All opening tags must have a corresponding closing tag, and elements must be properly nested (no overlapping).
Correct:text
Incorrect:
text
3. Case-Sensitive Tags
Tag names are case-sensitive. The opening and closing tags must match exactly in spelling and case.
4. Quoted Attribute Values
All attribute values must be enclosed in single or double quotes.
✅ ❌5. Unique Attributes in Elements
An element cannot have more than one attribute with the same name.
6. Escaping Special Characters
Certain characters like , and & must be escaped when used as text content.
Use: , &, ", 'Or wrap content in a block.
7. No Unpaired Markup Symbols
Characters such as This is invalid:
Must be:
8. Self-Closing Tags for Empty Elements
Empty elements should either use self-closing syntax or have separate opening and closing tags.
or ✅
❌Basically, if an XML document adheres to these rules, it is considered well-formed and can be parsed without error. Validity (conformance to a schema like DTD or XSD) is a separate requirement.
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