science

HCard

HCard 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 HCard rather than just read about it. In short: hCard is a microformat for publishing the contact details (which might be no more than the name) of people, companies, organizations, and places, in HTML, Atom, RSS, or arbitrary XML. The hCard microformat does this using a 1:1 representation of vCard (RFC 2426) properties and values, identified using HTML classes and rel attributes.

Key takeaways

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

Reference excerpt

hCard is a microformat for publishing the contact details (which might be no more than the name) of people, companies, organizations, and places, in HTML, Atom, RSS, or arbitrary XML. The hCard microformat does this using a 1:1 representation of vCard (RFC 2426) properties and values, identified using HTML classes and rel attributes. It allows parsing tools (for example other websites, or Firefox's Operator extension) to extract the details, and display them, using some other websites or mapping tools, index or search them, or to load them into an address-book program. In May 2009, Google announced that they would be parsing the hCard and hReview and hProduct microformats, and using them to populate search-result pages. In September 2010 Google announced their intention to surface hCard, hReview information in their local search results. In February 2011, Facebook began using hCard to mark up event venues.

Example Consider the HTML:

With microformat markup, that becomes:

A profile may optionally be included in the page header:

Here the properties fn, nickname, org (organization), tel (telephone number) and url (web address) have been identified using specific class names; and the whole thing is wrapped in class="vcard" which indicates that the other classes form an hcard, and are not just coincidentally named. If the hCard is for an organization or venue, the fn and org classes are used on the same element, as in <span class="fn org">Wikipedia</span> or <span class="fn org">Wembley Stadium</span>. Other, optional hCard classes also exist. It is now possible for software, for example browser plug-ins, to extract the information, and transfer it to other applications, such as an address book.

Geo and adr The Geo microformat is a part of the hCard specification, and is often used to include the coordinates of a location within an hCard. The adr part of hCard can also be used as a stand-alone microformat.

Live example Here are the Wikimedia Foundation's contact details as of February 2023, as a live hCard:

The mark-up (wrapped for clarity) used is:

In this example, the fn and org properties are combined on one element, indicating that this is the hCard for an organization, not a person.

Other attributes Other commonly used hCard attributes include

bday – a person's birth date email honorific-prefix honorific-suffix label – for non-granular addresses logo nickname note – free text photo post-office-box

See also vCard XHTML Friends Network FOAF

References

Further reading Allsopp, John (2007). Microformats: Empowering Your Markup for Web 2.0. Berkeley: Friendsof. p. 125. ISBN 978-1-59059-814-6. hCard 1.0 on microformats.org

Worked examples

Example 1 — a first encounter with HCard

Start with the simplest possible case. Write down what HCard 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 HCard 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 HCard 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 HCard

In research: HCard 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 HCard 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: HCard is common in secondary-school and first-year university syllabi. It links to neighbouring topics Business cards, Microformats, so understanding it makes those chapters shorter.
In everyday life: Look for HCard 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 HCard in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HCard 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 HCard out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HCard in simple terms?

Why does HCard 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 HCard?

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 HCard.