Validity vs. well-formedness: If an XML document does not conform to its DTD, should it be considered a “bad XML document”?

Introduction / Context:
XML distinguishes between well-formedness (syntactic correctness per XML 1.0 rules) and validity (conformance to a DTD or schema). Confusing these leads to incorrect error handling and validation assumptions.

Given Data / Assumptions:

• We consider a document with a referenced DTD.
• The document may or may not conform to that DTD.
• “Bad XML” is not a formal term; the standards speak of well-formed vs. valid.

Concept / Approach:
A document is well-formed if it obeys XML syntax: proper nesting, single root, quoted attributes, etc. It is valid if, in addition, it conforms to declarations in a DTD (or schema when using XSD). If a document does not conform to its DTD, it is invalid, but it can still be perfectly well-formed XML. Many XML workflows use schema validation instead of DTDs, or may not require validation at all.

Step-by-Step Solution:

Verification / Alternative check:
Most XML parsers offer a non-validating mode that still parses well-formed XML without consulting a DTD; failing validation does not make the XML unparsable.

Why Other Options Are Wrong:

• Calling the document “bad XML” conflates distinct concepts.
• Scope (internal vs external DTD) and namespaces do not change the definitions.

Common Pitfalls:
Expecting validation errors to be the same as syntax errors. They are different; fix accordingly.

Final Answer:
Incorrect: it is not DTD-valid, but it may still be well-formed XML