The Motive Web Design Glossary

validation

Validation is the process of checking data against a standard or requirement.

The term is commonly used when:

• quality assuring a webpage at a technical level (code validation), or
• checking the information entered by a person when sending information or using an online service (form validation).

Code validation

Webpage validation involves checking the code used to create a webpage (markup), against a computer-language specification.

A language specification sets out the parts of the language, and how the language can be used to write instructions that can be understood (processed or parsed) by a computer.

Languages commonly used to write (author) webpages include:

• Hypertext Markup Language (HTML)
• Extensible Hypertext Markup Language (XHTML)
• Extensible Markup Language (XML)
• Cascading Style Sheets (CSS)

Why validate?

• Validation provides an independent means of quality assuring webpage code; valid code is less likely to be ‘misunderstood’ by programs that are used to view webpages (web browsers).
• As use of the web evolves, and the features websites provide become more sophisticated, the integrity of the underlying code becomes more important—invalid code may ‘break’ a webpage.
• Valid code is easier to reinterpret and transform; new methods of accessing the web, such as mobile phones, benefit from different ‘views’ of webpage content; creating alternative views is easier when the underlying markup is standardised.

Checking webpage code with a validator

Code validation is typically carried out using an online (automated) service or validator.

For example the W3C Markup validation service can be used to validate HTML and XHTML.

For a webpage to be validated:

• the validation program must be able to link to the webpage
• the webpage must include a document-type declaration (DTD) that identifies the language used to markup content; if a DTD is not provided, the validator may ‘guess’ the language based on the markup used in the webpage

The validation process:

1. The author enters the address (URL) of the webpage to be validated.
2. A computer program checks that the webpage code conforms to the declared language.
3. If the code does not conform to the language specification (or is non-compliant), a report identifies potential errors.
4. The author corrects the code, and revalidates the webpage until no errors are found.

Tip: The W3C validator can also be activated by linking to the service from the webpage to be validated:

<a href="http://validator.w3.org/check?uri=referer">Validate HTML</a>

Test this webpage: Validate HTML

(The text Validate HTML is not required.)

Applied specification validation

An applied specification is a guide to creating web content for a specific user community.

For example the Web Accessibility Initiative (WAI), a working group of the W3C, has created Web Content Accessibility Guidelines (WCAG). These guidelines identify best-practices and techniques that enable people with disabilities equal-access to web content.

Compliance with an applied specification can also be evaluated. Cynthia is an online validator that identifies incorrect markup, additional markup requirements, and content that a webpage must contain to meet the WCAG checkpoints (and also United States disability law requirements as defined by Section 508).

It is important to note that automated applied-specification validation has its limitations. Guidelines can include checkpoints that are subjective and cannot be evaluated programmatically. For example, WCAG checkpoint 14.1:

14.1 Use the clearest and simplest language appropriate for a site’s content. [1]

Determining whether language used is ‘clear’, ‘simple’ or ‘appropriate’ can only be assessed by recruiting people who are familiar with the content domain, and who are also representative of the website’s intended audience.

Validation and accessibility: Complementary, not comparable

Valid markup does not necessarily make for accessible web content.

Specification-based validation is comparable to a grammar-check.

Specification-based validation is comparable to a grammar-check. Although words (elements) may be spelt correctly (use the correct tags) and be drawn from the same language, without appropriate grammar (structure) they can be meaningless.

For content to be accessible, the author must markup content into elements that convey the meaning of the content (semantic-markup).

Semantic markup can be used as a ‘hook’ by assistive technologies that enable users with disabilities to access web content, for example:

• using a screen reader, the H key can be used to move between headings to quickly scan the content of a webpage
• markup that is well-formed is more likely to be correctly interpreted by a screen reader
  Reference: Influence of valid code on screen readers (Joe Clark)

Related terms: authoring, markup, web accessibility, web standards

References and further reading

• [1] Techniques for Web Content Accessibility Guidelines 1.0 (WAI)
• Analysis and validation services (UITest.com)
  Directory of online services for checking webpages; including: accessibility, code validation, search engine optimisation, link integrity and download speed.
• HTML Tidy
  A tool for checking and cleaning markup.
• HTML validator for Firefox and Mozilla (Marc Gueury)
  Highly recommended: A tool that performs validation checks as you browse. At the bottom of your browser window an icon indicates code errors and warnings, and the steps you will need to take to create valid code (requires either Firefox or Mozilla).
• Quality assurance toolbox (W3C)
  Links to online validators including:
  • CSS validation service
  • [X(HTML)] markup validation service
• Validity and Accessibility (Gez Lemon, Juicy Studio)
  25 June 2005: A response to the Web Content Accessibility Guidelines working group’s proposed revision of the importance that should be assigned to valid code (from a level 1: mandatory or required to ensure a minimum level of accessibility, to a level 2: considered to enhance accessibility).
• Where our standards went wrong (Ethan Marcotte, A List Apart)
  The significance of code validation when creating websites may depend on defintions of ‘professionalism’ and balancing the realities of working commercially.

Form validation: Checking user-entered information

Form validation ensures that the user has provided sufficient information for a transaction to be completed. For online shopping systems this information typically includes first and last name, postal- and billing addresses and credit card details.

More sophisticated validation checks the integrity of the information provided; that the postal address exists, the credit card has not expired, etc.

Related terms: form, GUI

Further reading and references

• Communicating error messages accessibly (Peter Krantz, Standards-Smandards)

Motive Web Design Glossary Trivia