science

XHTML+RDFa

XHTML+RDFa is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand XHTML+RDFa rather than just read about it. In short: XHTML+RDFa (Extensible Hypertext Markup Language + Resource Description Framework in attributes) is an extended version of the XHTML markup language for supporting RDF through a collection of attributes and processing rules in the form of well-formed XML documents. XHTML+RDFa is one of the techniques used to develop Semantic Web content by embedding rich semantic markup.

Key takeaways

XHTML+RDFa belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect XHTML+RDFa to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of XHTML+RDFa from memory before moving on to harder problems.

Reference excerpt

XHTML+RDFa (Extensible Hypertext Markup Language + Resource Description Framework in attributes) is an extended version of the XHTML markup language for supporting RDF through a collection of attributes and processing rules in the form of well-formed XML documents. XHTML+RDFa is one of the techniques used to develop Semantic Web content by embedding rich semantic markup. Version 1.1 of the language is a superset of XHTML 1.1, integrating the attributes according to RDFa Core 1.1. In other words, it is an RDFa support through XHTML Modularization. RDFa in XHTML version 1.0 became a World Wide Web Consortium (W3C) Recommendation on 14 October 2008. The current recommendation is RDFa+XHTML version 1.1, which became a W3C Recommendation on 7 June 2012 and was updated with a ”Second Edition” on 22 August 2013 and a ”Third Edition” on 17 March 2015. Version 1.1 is based on XHTML™ 1.1 - Module-based XHTML - Second Edition. Version 1.0 was based on the first edition.

Overview Conventional Web documents contain large amounts of structured data that can be rendered in web browsers. This approach works fine for publishing purposes, however, a large amount of data stored in Web documents cannot be processed this way. XHTML+RDFa can provide machine-readable metadata within the markup code which makes additional user functionalities available. Most important of all, actions can be performed automatically that enables up-to-date publishing, structured search and sharing. RDFa can serve as a bridge between the "human and data webs". The potential in web documents enriched with RDFa is increasing since major search engines begin to process them while indexing. Yahoo indexes RDFa and microformats since 2008 and Google since 2009. The RDFa attribute specifications make it possible to describe structured data in any markup language. The RDFa markup in XHTML+RDFa reuses the markup code, thus eliminating the need for unnecessary duplications. XHTML+RDFa is not widely distributed yet, probably due to the lack of support in authoring tools and content management systems. However, there is good tendency. Drupal 7, for example, supports RDFa. Since the “a” in RDFa stands for attributes, it is straightforward to use CSS selectors to style the code.

Document Type Definition The combination of XHTML 1.1 and RDFa modules is claimed to be an example markup language. The Document Type Definition (DTD) is published at the W3C website. According to the document type declaration, the identifiers of an XHTML+RDFa document should look like the following:

An example XHTML+RDFa document:

Authoring The RDFa metadata is embedded as an XHTML attribute of the document element, generally the XHTML tag. The annotation syntax provided by RDFa can be used to express RDF statements in XHTML documents.

Validation XHTML+RDFa documents can be validated individually online at the W3C Markup Validation Service or together with CSS and RSS at W3C Unicorn. The validity of XHTML+RDFa documents can be indicated by the XHTML+RDFa conformance icons of W3C .

Examples XHTML syntax, additional namespaces and semantic markup.

See also HTML List of XML and HTML character entity references Microdata (HTML)

References

Worked examples

Example 1 — a first encounter with XHTML+RDFa

Start with the simplest possible case. Write down what XHTML+RDFa claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to XHTML+RDFa before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about XHTML+RDFa ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of XHTML+RDFa

In research: XHTML+RDFa appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses XHTML+RDFa in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: XHTML+RDFa is common in secondary-school and first-year university syllabi. It links to neighbouring topics HTML, Metadata publishing, Resource Description Framework, so understanding it makes those chapters shorter.
In everyday life: Look for XHTML+RDFa outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study XHTML+RDFa in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what XHTML+RDFa means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain XHTML+RDFa out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is XHTML+RDFa in simple terms?

Why does XHTML+RDFa matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study XHTML+RDFa?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on XHTML+RDFa.