Difference between revisions of "haudio"

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** '''title'''. required. text.
** '''title'''. required. text.
** '''collaborator'''. optional. [[hCard]].
** '''collaborator'''. optional. [[hCard]].
*** recognized roles: speaker, artist, band, publisher, label
*** recognized roles: speaker, artist, composer, band, publisher, label
** '''tracks'''. optional. using [[collection-id-pattern]].
** '''tracks'''. optional. using [[collection-id-pattern]].
** '''release-date'''. optional. using [[date-pattern]].
** '''release-date'''. optional. using [[date-pattern]].

Revision as of 00:35, 23 April 2007

hAudio 0.1

hAudio is a simple, open, distributed format, suitable for embedding information about audio recordings in (X)HTML, Atom, RSS, and arbitrary XML. hAudio is one of several microformats open standards.

hAudio Microformat Draft Specification 2007-04-18

Manu Sporny, Bitmunk - Digital Bazaar, Inc.
Manu Sporny, Bitmunk - Digital Bazaar, Inc.
Martin McEvoy
Alexandre Van De Sande
Michael Johnson
Dave Longley

Microformats copyright and patents statements apply.


It is difficult for a browser to extract semantic information about an audio recording described on a web page. Metadata such as speaker, musician, publisher, label, title of the work, release date, acquisition link, related image artwork and tags provide relevant context for the audio recording.

Having such information marked up can provide a number of benefits to the viewer. If a web browser understands that a particular web page contains a song performed by an artist, it can produce richer interactions. For example, specific searches may be performed for artists and songs via general search services such as Google and Wikipedia. Specific search services may also be queried such as MusicBrainz, The Internet Archive, FreeDB, or Bitmunk. Additionally, classification by crawlers can become more accurate. If there are 20 tracks found on a page done by the same artist, and that content consumes a significant portion of the page, it can be assumed that the page is not only about music, but also about a particular artist.

In order to enable and encourage the sharing, distribution, syndication, and aggregation of audio content, the authors propose the hAudio microformat, an open standard for distributed audio metadata. The authors have researched both numerous audio-info-examples in the wild and earlier attempts at audio-info-formats, and have designed hAudio around a simple minimal schema for audio content. Feedback is encouraged on the hAudio feedback page.

Inspiration and Acknowledgments

Many thanks to the various individuals that did research and proposed ideas and discussion related to media info and audio info in general. Among the many participants are RodBegbie, Dean Hudson, Çelik, Mary Hodder (http://napsterization.org/stories/), Joshua Kinberg (http://joshkinberg.com/blog/), ChrisMessina, and Lisa Rein (http://onlisareinsradar.com/).


Audio content consistently share several common fields. Where possible hAudio has been based on this minimal common subset.

Out of scope

Fields that are type-specific have been omitted from hAudio. It is important that hAudio be kept simple and minimal from the start. Additional features can be added as deemed necessary by practical implementation experience.

The concept of a universal audio identifier, that is, how to identify the same audio album, song, speech, or podcast across different music and audio sites, though something very useful to have, is outside the scope of this format.

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


In General

The hAudio format is based on a set of fields common to numerous audio content sites and formats in use today on the web. Where possible field names have been chosen based on those defined by the related hCard standards.


The hAudio schema consists of the following:

  • hAudio (haudio)
    • title. required. text.
    • collaborator. optional. hCard 1.0.
      • recognized roles: speaker, artist, composer, band, publisher, label
    • tracks. optional. using collection-id-pattern.
    • release-date. optional. using Date Design Pattern.
    • sample. optional. using rel-sample.
    • acquire. optional. using rel-acquire or rel-payment.
    • image-summary. optional. using img.
    • genre. optional. text.
    • length. optional. time in units. abbr-pattern.
    • price. optional. hCurrency.

Field details

The fields of the hAudio schema represent the following:

The following field names have been reused from the hCard and hCalendar microformats: version, summary, fn, url, photo, description. In addition, items and reviewers described by hCards MAY contain any hCard field. The rel value "self" has been reused from the Atom 1.0 specification.

More Semantic Equivalents

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

  • For any "url", use <a class="url" href="...">...</a> inside the element with the class name 'haudio' in hAudio.
  • And for "image-summary", use <img class="image-summary" src="..." alt="Photo of ..." />


  • To explicitly convey the natural language that an hAudio is written in, use the standard (X)HTML 'lang' attribute on the element with class="haudio", e.g. <div class="haudio" lang="en"> ... </div> If portions of an hAudio (e.g. the item name) are in a different language, use the 'lang' attribute on those portions.
  • hAudio processors which need to handle the language of reviews MUST process the standard (X)HTML 'lang' attribute as specified.

Human vs. Machine Readable

If an <abbr> element is used for a property, then its 'title' attribute is used for the value of the property, instead of the contents of the element, which can then be used to provide a user-friendly alternate presentation of the value.

Similarly, if an <img /> element is used for one or more properties, it MUST be treated as follows:

  1. For the "image-summary" 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.

Object Includes

hAudio includes support for the id-based-collection-pattern.


This section is informative.

  • By marking up audio content with the hAudio microformat, the expectation is communicated that information about the content MAY be indexed. This has no impact on the copyright of the content itself which the publisher may explicitly specify using rel="license" as specified above.
  • The enumerated list of item types is under development and may be extended.
  • Each type may have custom hAudio fields that follow the common set.
  • Additional details about a particular item should be specified with the rest of the item's info at the URL provided for the item.


Here are a few examples of audio content from current web sites, and how they could be easily enhanced to support the hAudio audio metadata microformat.

Want to write valid hAudio? Use the hAudio creator to write about audio content and publish it on your blog.

Speech example

Song example

Album example

Podcast example

Examples in the wild

This section is informative.


This section is informative.

See hAudio Implementations.


Normative References

Informative References

Similar Work


This specification is (C) 2005 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.


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

Work in progress

This specification is a work in progress. As additional aspects are discussed, understood, and written, they will be added.

Further Reading

See also

Related Pages