hcard

From Microformats Wiki
Revision as of 00:56, 23 April 2006 by Tantek (talk | contribs) (→‎Human vs. Machine readable: - tweak Keri's additions, add more special case elements etc. from hcard-parsing)
Jump to navigation Jump to search

hCard

hCard is a simple, open, distributed contact information format for people, companies, and organizations, which is suitable for embedding in (X)HTML, Atom, RSS, and arbitrary XML. hCard is a 1:1 representation of the vCard standard (RFC2426) in XHTML, one of several open microformat standards.

Want to get started with writing an hCard? Use the hCard creator to write up some contact information and publish it.

Draft Specification

Editor

Tantek Çelik, Technorati, Inc.

Authors

Copyright

This specification is (C) 2004-2024 by the authors. However, the authors intend to submit (or already have submitted, see details in the spec) this specification to a standards body with a liberal copyright/licensing policy such as the GMPG, IETF, and/or W3C. Anyone wishing to contribute should read their copyright principles, policies and licenses (e.g. the GMPG Principles) and agree to them, including licensing of all contributions under all required licenses (e.g. CC-by 1.0 and later), before contributing.

Patents

This specification is subject to a royalty free patent policy, e.g. per the W3C Patent Policy, and IETF RFC3667 & RFC3668.

Inspiration and Acknowledgments

Thanks to: my good friend Vadim who introduced me to vCard many years ago, and if I'd only paid more attention then, perhaps I could have helped a lot of people avoid wasting a lot of time reinventing various standards wheels.

Introduction

The vCard standard (RFC2426), has been broadly interoperably implemented (e.g. Apple's "Address Book" application built into MacOSX).

In addition, many bloggers identify themselves by name and discuss their friends and family. With just a tad bit of structure, bloggers can discuss people in their blog(s) in such a way that spiders and other aggregators can retrieve this information, automatically convert them to vCards, and use them in any vCard application or service.

This specification introduces the hCard format, which is a 1:1 representation of the aforementioned vCard standard, in semantic XHTML. Bloggers can both embed vCards directly in their web pages, and style them with CSS to make them appear as desired. In addition, hCard enables applications to retrieve information about such vCards directly from web pages without having to reference a separate file.

Use the hCard creator, copy the HTML code it generates to your blog or website to publish your contact info.

Semantic XHTML Design Principles

Note: the Semantic XHTML Design Principles were written primarily within the context of developing hCard and hCalendar, thus it may be easier to understand these principles in the context of the hCard design methodology (i.e. read that first). Tantek

XHTML is built on XML, and thus XHTML based formats can be used not only for convenient display presentation, but also for general purpose data exchange. In many ways, XHTML based formats exemplify the best of both HTML and XML worlds. However, when building XHTML based formats, it helps to have a guiding set of principles.

  1. Reuse the schema (names, objects, properties, values, types, hierarchies, constraints) as much as possible from pre-existing, established, well-supported standards by reference. Avoid restating constraints expressed in the source standard. Informative mentions are ok.
    1. For types with multiple components, use nested elements with class names equivalent to the names of the components.
    2. Plural components are made singular, and thus multiple nested elements are used to represent multiple text values that are comma-delimited.
  2. Use the most accurately precise semantic XHTML building block for each object etc.
  3. Otherwise use a generic structural element (e.g. <span> or <div>), or the appropriate contextual element (e.g. an <li> inside a <ul> or <ol>).
  4. Use class names based on names from the original schema, unless the semantic XHTML building block precisely represents that part of the original schema. If names in the source schema are case-insensitive, then use an all lowercase equivalent. Components names implicit in prose (rather than explicit in the defined schema) should also use lowercase equivalents for ease of use. Spaces in component names become dash '-' characters.
  5. Finally, if the format of the data according to the original schema is too long and/or not human-friendly, use <abbr> instead of a generic structural element, and place the literal data into the 'title' attribute (where abbr expansions go), and the more brief and human readable equivalent into the element itself. Further informative explanation of this use of <abbr>: Human vs. ISO8601 dates problem solved

Format

In General

The vCard standard (RFC2426) forms the basis of hCard.

The basic format of hCard is to use vCard object/property names in lower-case for class names, and to map the nesting of vCard objects directly into nested XHTML elements.

More Semantic Equivalents

However, for some properties there is a more semantic equivalent, and therefore they get special treatment, e.g.:

  • URL in vCard becomes <a class="url" href="...">...</a> inside the element with class="vcard" in hCard.
  • Similarly, EMAIL in vCard becomes <a class="email" href="mailto:...">...</a>
  • PHOTO in vCard becomes <img class="photo" src="..." alt="Photo of ..." /> or <object class="photo" data="..." type="...">Photo of ...</object>
  • UID in vCard simply becomes another semantic applied to a specific URL (or EMAIL) for an hCard.

Singular vs. Multivalued Properties

For properties which are singular (e.g. "N" and "FN"), the first descendant element with that class should take effect, any others being ignored.

For properties which can be plural (e.g. "TEL"), each class instance should create a instance of that property. Plural properties with subtypes (e.g. TEL with WORK, HOME, CELL) can be optimized to share a common element for the property itself, with each instance of subtype being an appropriately classed descendant of the property element.

Plural Properties Singularized

Since plural property names become their singular equivalents, even if the original plural property permitted only a single value with multiple components, those multiple components are represented each with their own singularly named property and the the property is effectively multivalued and subject to the above treatment of multivalued properties.

Human vs. Machine readable

If an <abbr> element is used for a property, then the 'title' attribute of the <abbr> element is the value of the property, instead of the contents of the element, which instead provide a human presentable version of the value.

If an <a> element is used for one or more properties, it must be treated as follows:

  1. For the "PHOTO" property and any other property that takes a URL as its value, the href="..." attribute provides the property value.
  2. For other properties, the element's content is the value of the property.

If an <img> element is used for one or more properties, it must be treated as follows:

  1. For the "PHOTO" property and any other property that takes a URL as its value, the src="..." attribute provides the property value.
  2. For other properties, the <img> element's 'alt' attribute is the value of the property.

If an <object> element is used for one or more properties, it must be treated as follows:

  1. For the "PHOTO" property and any other property that takes a URL as its value, the data="..." attribute provides the property value.
  2. For other properties, the element's content is the value of the property.

Value excerpting

Sometimes only part of an element which is the equivalent for a property should be used for the value of the property. This typically occurs when a property has a subtype, like TEL. For this purpose, the special class name "value" is introduced to excerpt out the subset of the element that is the value of the property. E.g. here is an hCard fragment for marking up a home phone number: 

<span class="tel">
 <span class="type">home</span>:
 <span class="value">+1.415.555.1212</span>
</span>

This hCard fragment could be displayed as: 

home: +1.415.555.1212


Property Exceptions

vCard has several properties which either do not make sense on, or are already implied within the context of a web page. This section explains what to (not) do with them.

  1. NAME, PROFILE, SOURCE, PRODID, VERSION properties as defined in Sections 2.1.2, 2.1.3, 2.1.4, 3.6.3, 3.6.9 of RFC 2426. Content publishers MUST NOT use these properties in their hCards, and as such, hCard consumers/parsers MUST IGNORE these properties if they are found within an hCard. Instead. hCard to vCard converters SHOULD use the title of the page where the hCard is found (e.g. the <title> element in (X)HTML documents) to construct the NAME property, MAY output a PROFILE value of "VCARD" per RFC 2426, SHOULD use the URL of the page where the hCard is found to construct the SOURCE property (e.g. perhaps as a parameter to a URL/service that converts hCards to vCards), for an output vCard stream (e.g. a .vcf file). Only services/applications that output actual vCards should write the PRODID property, with the product identifier for said service/application. Similarly only such services/applications should write the VERSION property, with the value "3.0" (without quotes) per RFC2426 Section 3.6.9.

Organization Contact Info

If the "FN" and "ORG" properties have the exact same value (typically because they are set on the same element, e.g. class="fn org"), then the hCard represents contact information for a company or organization and should be treated as such. In this case the author MUST also NOT set the "N" property, or set it (and any sub-properties) explicitly to the empty string "". Thus parsers should handle the missing "N" property in this case by implying empty values for all the "N" sub-properties.

Implied "n" Optimization

Although vCard requires that the "N" property be present, the authors of the vCard specification (RFC 2426) themselves do not include "N" properties in their vCards near the end of the spec (p.38). This apparent contradiction can be resolved by simply allowing the "FN" property to imply "N" property values in typical cases provided in the spec. We do so explicitly in hCard.

If "FN" and "ORG" are not the same (see previous section), and the value of the "FN" property is exactly two words (separated by whitespace), and there is no explicit "N" property, then the "N" property is inferred from the "FN" property. For "FN"s with either one word see below, and for three or more, the author MUST explicitly markup the "N", except for the organization contact info case, see above for that.

  1. The content of "FN" is broken into two "words" separated by whitespace.
  2. The first word of the "FN" is interpreted as the "given-name" for the "N" property.
  3. The second/last word of the "FN" is interpreted as the "family-name" for the "N" property.
  4. Exception: If the first word ends in a "," comma OR if the second word is a single character (optionally followed by a period "."), then the first word (minus the comma at the end if any) is interpreted as the "family-name" and the second word is interpreted as the "given-name".

This allows simplification in the typical case of people stating:

  • given-name (space) family-name
  • family-name (comma) given-name
  • family-name (comma) given-name-first-initial
  • family-name (space) given-name-first-initial (optional period)

Implied "nickname" Optimization

Due to the prevalence of the use of nicknames/handles/usernames on the Web in actual content published on the Web (e.g. authors of reviews), hCard also has an implied "nickname" optimization to handle this.

Similar to the implied "n" optimization, if "FN" and "ORG" are not the same, and the value of the "FN" property is exactly one word, and there is no explicit "N" property, then:

  1. The content of the "FN" is treated as a "nickname" property value.
  2. Parsers should handle the missing "N" property by implying empty values for all the "N" sub-properties.

Note: the hCard may have additional explicit "nickname" property values in addition to the implied nickname.

Implied "organization-name" Optimization

The "ORG" property has two subproperties, organization-name and organization-unit. Very often authors only publish the organization-name. Thus if an "ORG" property has no "organization-name" inside it, then its entire contents MUST be treated as the "organization-name".

Root Class Name

The root class name for an hCard is "vcard".

Property List

This is the list of properties (and subproperties, in parentheses, like this) in hCard, taken from vCard:

  • fn, n (family-name, given-name, additional-name, honorific-prefix, honorific-suffix), nickname, sort-string
  • url, email (type, value), tel (type, value)
  • adr (post-office-box, extended-address, street-address, locality, region, postal-code, country-name, type, value), label
  • geo (latitude, longitude), tz
  • photo, logo, sound, bday
  • title, role, org (organization-name, organization-unit)
  • category, note
  • class, key, mailer, uid, rev

type subproperty values

The 'type' subproperty in particular takes different values depending on which property it is a subproperty of. These 'type' subproperty values are case-INSENSITIVE, meaning "Home" is the same as "home", as well as multivalued, e.g. a tel can be home and preferred: 

<span class="tel"><span class="type">Home</span> (<span class="type">pref</span>erred):
 <span class="value">+1.415.555.1212</span>
</span>

The following lists are informative. See RFC2426 sections 3.2.1 ADR, 3.3.1 TEL, and 3.3.2 EMAIL respectively for normative type values. They are repeated here for convenience. Default type subproperty value(s) is(are) first in each list and indicated in ALL CAPS. types may be multivalued.

  • adr type: INTL, POSTAL, PARCEL, WORK, dom, home, pref
  • tel type: VOICE, home, msg, work, pref, fax, cell, video, pager, bbs, modem, car, isdn, pcs
  • email type: INTERNET, x400, pref, "other IANA registered address types"

XMDP Profile

See hcard-profile for the XMDP profile of hCard which contains the above complete list of properties, with references to their RFC 2426 definitions.

Parsing Details

See hCard parsing.

Examples

This section is informative.

Sample vCard

Here is a sample vCard: 

BEGIN:VCARD
VERSION:3.0
N:Çelik;Tantek
FN:Tantek Çelik
URL:http://tantek.com/
ORG:Technorati
END:VCARD

and an equivalent in hCard with various elements optimized appropriately. See hCard Example 1 for the derivation. 

<div class="vcard">
 <a class="url fn" href="http://tantek.com/">Tantek Çelik</a>
 <div class="org">Technorati</div>
</div>

This hCard might be displayed as:

Tantek Çelik
Technorati

Note: The version information is unnecessary in hCard markup directly since the version will be defined by the profile of hCard that is used/referred to in the 'profile' attribute of the <head> element.

More Examples

See hcard-examples for more examples, including all examples from vCard RFC 2426 converted into hCard.

Examples in the wild

This section is informative.

The following sites have published hCards, and thus are a great place to start for anyone looking for examples "in the wild" to try parsing, indexing, organizing etc. If you have an hCard on your own page, feel free to add it to the top of this list. Once the list grows too big, we'll make a separate wiki page.

New Examples

Please add new examples to this section.

Examples

Examples with some problems

  • Gerard Braad has published an example on his profile page that is almost consistent with his original vCard file. Also progress is made for transforming his FoaF file to a hCard encoded representation. (also done for my spouse:Yong Yuan)
    • (2005-09-27) PASSED, PASSED
    • WARNINGS
      • uses 'n given-name' and 'n family-name' instead of nesting the given- and family- names inside the 'n'
      • has one 'tel' value with a bunch of values stuffed in
      • probably more problems --RyanKing 17:19, 5 Jan 2006 (PST)
  • Cori Schlegel discusses how he has updated his contact page with hCard
    • INVALID - using 'prefix' instead of 'honorific-prefix' and type's in classnames (in both adr and tel) and has two photo's (the second could be 'logo') --RyanKing 15:15, 5 Jan 2006 (PST)
  • The good ship Leonid Miloslavskiy spotted in the North Atlantic
    • INVALID --RyanKing 00:50, 27 Oct 2005 (PDT)
      • class="family" should probably be family-name
      • the "n" property is missing and the "n" optimization can't be applied
      • the first geo propery is empty, the second one is invalid (ie, it doesn't contain lat/long)
  • Landsbanki Føroya
    • INVALID - using embedded rdf/xml invalidly
  • Chris Cherry's contact page with his hCard
    • WARNING - uses class="cell" instead of <span class="type">cell</span>
  • University of Bath Person Finder results are encoded with hCards so you can easily create a vCard from any result.
    • ERROR - attempt to use Implied-N optimization where that's not possible. --RyanKing 14:29, 5 Jan 2006 (PST)
    • Error appears for external users only. Won't be fixed any time soon. -- PhilWilson 00:03, 28 Jan 2006 (GMT)
  • Richi Jennings has put up his attempt
    • INVALID, missing FN --RyanKing 12:47, 5 Jan 2006 (PST)
  • shifting pixel photoblog has published an hCard.
    • "organization_name" should be "organization-name" (s/_/-/), otherwise good --RyanKing 14:01, 5 Jan 2006 (PST)

Implementations

This section is informative.

The following implementations have been developed which either generate or parse hCards. If you have an hCard implementation, feel free to add it to the top of this list. Once the list grows too big, we'll make a separate wiki page.

Additional Applications

This section is informative.

There are numerous potential additional uses and applications for hCards on the Web. The following are merely a few thoughts and possibilities that folks have come up with:

  • As an open standard/format for Gravatars.
  • Marking up individual authors of blog posts on a group blog
  • Marking up people's names and URLs in a blogroll
  • Any reference to people in blog posts (e.g. when citing them, or referencing them, or describing them, by name).
  • ...

References

Normative References

Informative References

Specifications That Use hCard

Similar Work

Related Pages

  • hCard FAQ - If you have any questions about hCard, check here, and if you don't find answers, add your questions!
  • hCard parsing - Normatively details of how to parse hCards.
  • hCard issues - Please add any issues with the specification to the issues page.
  • hCard profile - The XMDP profile for hCard

This specification is a work in progress. As additional aspects are discussed, understood, and written, they will be added. These thoughts, issues, and questions are kept in separate pages.

  • hCard Brainstorming - where we are keeping our brainstorms and other explorations relating to hCard
  • hCard tests - a wiki page with actual embedded hCards to try parsing.

Further Reading

Retrieved from "http://microformats.org/wiki/index.php?title=hcard&oldid=6055"