Ensuring that Web pages are well-formed

Important Information about Techniques

See Understanding Techniques for WCAG Success Criteria for important information about the usage of these informative techniques and how they relate to the normative WCAG 2.1 success criteria. The Applicability section explains the scope of the technique, and the presence of techniques for a specific technology does not imply that the technology can be used in all situations to create content that meets WCAG 2.1.

Applicability

Any XML-based markup languages.

This technique relates to Success Criterion 4.1.1: Parsing (Sufficient as a way to meet an unwritten technique).

Description

The objective of this technique is to avoid key errors that are known to cause problems for assistive technologies when they are trying to parse contents. Well-formedness is checked by parsing the document with a conforming XML parser and checking if the validation report mentions well-formedness errors. Every conforming XML parser is required to check well-formedness and stop normal processing when a well-formedness error is found (a conforming XML parser does not need to support validation).

Examples

Example 1

XML files include a document type declaration, a xsi:schemaLocation attribute or other type of reference to a schema. The developer can use off-line or online validators, an XML editor or an IDE with XML support (see Resources below) to check well-formedness.

Example 2

When XML files do not include a document type declaration, a xsi:schemaLocation attribute or a processing instruction referencing a schema even though there is a schema for them, the relevant schema is specified by a command line instruction, a user dialog or a configuration file, and the XML files are checked against the schema.

Example 3

When XML files do not include a document type declaration, a xsi:schemaLocation attribute or a processing instruction referencing a schema even though there is a schema for them, the namespace is dereferenced to retrieve a schema document or resource directory (Resource Directory Description Language: RDDL), and the XML files are checked against the schema.

Example 4

When a Website generates XML dynamically instead of serving only static documents, a developer can use XMLUnit, XML Test Suite or a similar framework to test the generated XML code.

Resources

Resources are for information purposes only, no endorsement implied.

For other resources, see G134: Validating Web pages.

Tests

Procedure

  1. Load each file into a validating XML parser.
  2. Check that there are no well-formedness errors.

Expected Results

Step 2 is true.