hatom

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hAtom

hAtom is a microformat for content that can be syndicated, primarily but not exclusively weblog postings. hAtom is based on a subset of the Atom syndication format.

This microformat is a draft; please address your concerns, issues, comments, etc. in hatom-issues.

Draft Specification

Editor/Author

Contributors

Copyright

This specification is (C) 2005-2024 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.

Introduction

@TODO - we need an intro here

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 Atom Syndication Format provides the conceptual basis for this microformat, with the following caveats:

  • Atom provides a lot more functionality that we need for a "blog post" microformat, so we've taken the minimal number of elements needed.
  • the "logical" model of hAtom is that of Atom. If there is a conflict, Atom should be taken as correct.
  • the "physical" model of hAtom -- the actual writing of elements -- is a lot more varied than Atom provides for, due to the variety of ways weblogs are actually produced in the wild. The hAtom microformat provides a number of rules for "bridging the gap"

Schema

Schema elements are based on the Atom nomenclature and follow the microformat pattern of prefixing a unique identifier (in this case, 'h') on the outermost container elements -- the Feed or Entry. The parts of this microformat are based on analysis of many weblog, bulletin board and media posts and can be read blog-post-brainstorming#Discovered_Elements.

Rules and Definitions

See the Nesting Rules section above for placement of these elements.

Feed
Entry
  • an Entry element is identified by class="hentry"
  • an Entry element represents the concept of an atom entry
  • a weblog entry MUST be enclosed in a single Entry element
Entry Title
  • an Entry Title element is identified by the class name headline
  • an Entry Title element may alternately be identified by the <h#> element in an Entry
  • an Entry Title element represents the concept of an atom entry title
  • otherwise the Entry Title is the empty string
Entry Content
  • an Entry Content element is identified by class="content"
  • an Entry Content element represents the concept of an atom content
  • an Entry MAY have 0 or more Entry Content elements
We recognize this varies from the Atom spec: see the next rule.
  • the "logical Entry Content" of an Entry is the concatenation, in order of appearance, of all the Entry Contents within the Entry
Many weblogs split content into multiple sections with a "Read More" link and javascript tricks. This is also needed in cases where Entry Titles are coded inline and are considered part of the content.
  • the "logical Entry Content" MUST be complete; that is, contain the entire content of the Entry
Otherwise it should be marked as Entry Summary.
Entry Summary
  • an Entry Summary element is identified by class="excerpt"
  • an Entry Summary element represents the concept of an atom summary
  • an Entry MAY have 0 or more Entry Summary elements
We recognize this varies from the Atom spec: see the next rule.
  • the "logical Entry Summary" of an Entry is the concatenation, in order of appearance, of all the Entry Summarys within the Entry
Entry Permalink
  • an Entry Permalink element is identified by rel="bookmark"
  • an Entry Permalink element represents the concept of an atom link in an entry
  • Entry Permalinks SHOULD be absolute URIs
  • Entry Permalinks MUST be the same as the atom:link (or rss:link) used in syndication feeds
The intention of the previous two rules to gently force people to use strings that can be byte compared for equivalence. In general, the canonical URI should be the link used in an Atom entry.
  • if an Entry has multiple elements marked as the Entry Permalink, they MUST have exactly the same URI
  • an Entry SHOULD have an Entry Permalink
  • there can be at most 1 Entry in an XHTML document without an Entry Permalink; the Entry Permalink of this Entry is the URI of the page
This rule is needed for media pages (i.e. a news article on cnn.com). There is some ugliness of with this because the URI could be non-canonical.
Disambiguation
  • The first valid element in an Entry marked as an Entry Permalink is the Entry Permalink
Entry Published
  • an Entry Published element is identified by the class name published
  • a Entry Published element represents the concept of atom published
  • the machine readable datetime should be encoded with an <abbr> element using the datetime-design-pattern; the machine readable datetime should be complete, that is, specified to the second with the timezone included
This is to be consistent with the Atom Datetime Construct.
  • optionally, this can be specified by an HTML element with the ISO datetime in the text.
Disambiguation
  • The first valid element in an Entry marked as an Entry Published is the Entry Published element
Entry Updated
  • an Entry Updated element is identified by class="updated"
  • a Entry Updated element represents the concept of atom updated
  • the machine readable datetime should be encoded with an <abbr> element using the datetime-design-pattern; the machine readable datetime should be complete, that is, specified to the second with the timezone included
This is to be consistent with the Atom Datetime Construct.
  • if there is no Entry Updated element, the value is assumed to be that of Entry Published
Entry Published is more often available in weblog templates, so we're going with that.
  • if there is no Entry Updated and Entry Published elements, transformation to Atom is problematic
This is because a published element is required. Suggestions would be appreciated here.
  • optionally, this can be specified by an HTML element with the ISO datetime in the text.
This is a little uglier for the reader, but it's possible.
Disambiguation
  • The first valid element in an Entry marked as an Entry Updated is the Entry Updated element
Entry Author
  • an Entry Author element is represented by class="author"
  • an Entry Author element SHOULD use an XHTML <address> element
  • an Entry Author element represents the concept of an atom author
  • an Entry Author element SHOULD contain an hCard
If it does not, just consider the text to effectively be the FN. hReview also considers a hCard to be a SHOULD, not a MUST.
  • an Entry MAY have 0 or more Entry Author elements
  • if an Entry has 0 Entry Author elements, the "logical Entry Author" is assumed to be the author of the XHTML page
Atom requires at least one Author

Categories and Tags

This section needs a lot more work.

  • Entry categories and tagging are represented by rel-tag
  • rel-tag elements may appear anywhere within a Entry, including Entry Content. This is the one case where we break opacity.

XMDP Profile

<dl class="profile">
 <dt>class</dt>
 <dd><p>
  <a rel="help" href="http://www.w3.org/TR/html401/struct/global.html#adef-class">
   HTML4 definition of the 'class' attribute.</a>
  This meta data profile defines some 'class' attribute values (class names) 
  and their meanings as suggested by a 
  <a href="http://www.w3.org/TR/WD-htmllink-970328#profile">
   draft of "Hypertext Links in HTML"</a>.
  <dl>
   <dt>hfeed</dt>
   <dd>
    The concept of atom:feed from 
    <a href="http://www.atomenabled.org/developers/syndication/atom-format-spec.php">The Atom Syndication Format</a>, 
    constrained and modified as per the <a href="http://microformats.org/wiki/hatom">hAtom microformat spec</a>.
   </dd>
   <dt>hentry</dt>
   <dd>
    The concept of atom:entry from 
    <a href="http://www.atomenabled.org/developers/syndication/atom-format-spec.php">The Atom Syndication Format</a>, 
    constrained and modified as per the <a href="http://microformats.org/wiki/hatom">hAtom microformat spec</a>.
   </dd>
   <dt>content</dt>
   <dd>
    The concept of atom:content from 
    <a href="http://www.atomenabled.org/developers/syndication/atom-format-spec.php">The Atom Syndication Format</a>, 
    constrained and modified as per the <a href="http://microformats.org/wiki/hatom">hAtom microformat spec</a>.
   </dd>
   <dt>excerpt</dt>
   <dd>
    The concept of atom:summary from 
    <a href="http://www.atomenabled.org/developers/syndication/atom-format-spec.php">The Atom Syndication Format</a>, 
    constrained and modified as per the <a href="http://microformats.org/wiki/hatom">hAtom microformat spec</a>.
   </dd>
   <dt>bookmark</dt>
   <dd>
    The concept of atom:link (without any "rel") with an atom:entry from 
    <a href="http://www.atomenabled.org/developers/syndication/atom-format-spec.php">The Atom Syndication Format</a>, 
    constrained and modified as per the <a href="http://microformats.org/wiki/hatom">hAtom microformat spec</a>.
   </dd>
   <dt>published</dt>
   <dd>
    The concept of atom:published from 
    <a href="http://www.atomenabled.org/developers/syndication/atom-format-spec.php">The Atom Syndication Format</a>, 
    constrained and modified as per the <a href="http://microformats.org/wiki/hatom">hAtom microformat spec</a>.
   </dd>
   <dt>updated</dt>
   <dd>
    The concept of atom:updatedfrom 
    <a href="http://www.atomenabled.org/developers/syndication/atom-format-spec.php">The Atom Syndication Format</a>, 
    constrained and modified as per the <a href="http://microformats.org/wiki/hatom">hAtom microformat spec</a>.
   </dd>
   <dt>author</dt>
   <dd>
    The concept of atom:author from 
    <a href="http://www.atomenabled.org/developers/syndication/atom-format-spec.php">The Atom Syndication Format</a>, 
    constrained and modified as per the <a href="http://microformats.org/wiki/hatom">hAtom microformat spec</a>.
   </dd>
  </dl>
 </dd>
</dl>


Examples

See hatom-examples.

Examples in the wild

This section is informative.

Implementations

This section is informative.

References

Normative References

Informative References

Specifications That Use hAtom

Similar Work

Work in progress

This specification is a work in progress. As additional aspects are discussed, understood, and written, they will be added. There is a separate document where we are keeping our brainstorms and other explorations relating to hAtom:


Discussions

Q&A

  • If you have any questions about hAtom, check the hAtom FAQ, and if you don't find answers, add your questions!

Issues

  • Please add any issues with the specification to the separate hAtom issues document.

Recent Changes

Most recent at top please. This section will eventually be removed but should be helpful for people tracking changes during specing.

  • Entry Permalink now SHOULD (as opposed to MUST) be a complete URI
  • Entry Title now preferentially uses class="title"
  • Entry Author most explicitly be marked class="author"
  • using an <address around Entry Author and Entry Contributor is no longer required

See Also

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