hAtom

hAtom is a microformat for content that can be syndicated, primarily but not exclusively weblog postings. hAtom is a strongly based on a subset of the Atom syndication format; every concept in hAtom has a corresponding definition in Atom.

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

Draft Specification

Editor

David Janes, BlogMatrix, Inc.

Authors

David Janes, BlogMatrix, Inc

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

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.

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.
Use the most accurately precise semantic XHTML building block for each object etc.
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>).
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.
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

Schema

Schema elements are based on the Atom nomenclature and follow the microformat pattern of prefixing a unique identifier (in this case, atom) 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. Note the renaming of 'EntryGroup' to 'Feed' to be more consistent with Atom ternminology.

Nomenclature

Concept	Atom Identifier	hAtom Microformat Usage
Feed	`atom:feed`	add `class="feed"`; OR implicit in the XHTML page
Feed Title	`atom:title`	Not defined in the first iteration of this proposal.
Feed Permalink	`atom:link@rel=alternate`	Not defined in the first iteration of this proposal.
Entry	`atom:entry`	Add `class="entry"`; if practical, also define `id="unique-identifier"` to the Entry.
Entry Title	`atom:title`	Use `<h#>` in block elements; OR non-preferentially add `class="title"` in inline elements.
Entry Content	`atom:content`	Add `class="content"` to all appropriate blocks. Multiple Entry Content blocks are logically considered one concatenated `atom:content` equivalent.
Entry Summary	`atom:summary`	Add `class="summary"` to all appropriate blocks. Multiple Entry Summary blocks are logically considered one concatenated `atom:summary` equivalent.
Entry Permalink	`atom:link`	Add `rel="bookmark"`.
Entry Published	`atom:published`	Use `<abbr class="published" title="YYYYMMYYThh:mm:ss±ZZ:ZZ">`...`</abbr>`, following the datetime-design-pattern.
Entry Author	`atom:author`	Use `<address class="author">`...`</address>`. Adding a hCard is highly recommended.

Nesting Rules

Concept	Nests In	hAtom Opaque	Cardinality	Logical Cardinality
Feed	HTML document	No	0-N	1
Entry	Feed HTML document	No	0-N	0-N
Entry Title	Entry Entry Permalink	No	0-N	0-1
Entry Content	Entry	Yes	0-N	0-1
Entry Summary	Entry	Yes	0-N	0-1
Entry Permalink	Entry Entry Title Entry Published	No	0-N	1
Entry Published	Entry Entry Permalink	No	0-N	0-1
Entry Author	Entry	Yes	0-N	0-N

hAtom Opaque

"hAtom Opaque" specifies whether a hAtom parser should "look inside" the element for further hAtom content. If there are multiple rules applied to the same element take the OR of the two (i.e. "Yes" always wins)

hAtom Opaque is designed to make parsing rules less ambiguous. In particular, it allows "quoted" hAtom elements (from another blog being blockquoted, for example) ti be ignored. It also allows 'embedded' hAtom to be potentially delivered within hAtom itself, and to prevent accidental 'leaking' of other microformat information up into the hAtom container.

Cardinality

How many times can an element of the given type appear in it's nesting element in the XHTML document.

Logical Cardinality

From a modeling/logical perspective, how many times can an element appear.

This is all rule dependent, see below. For example, an Entry Permalink may appear 6 times, but each one must be the same value; an Entry Content element may appear 3 times, but they are all concatenated together to make a single logical element.

Rules and Definitions

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

Feed

an XHTML Feed element is identified by class="feed"
a Feed element represents the concept of an atom feed

In particular, as a container for Entrys.

if there is no Feed element on a page, the "logical Feed" is assumed to be the XHTML document
hAtom documents MAY have multiple, non-nested Feed elements

This may happen on news pages, or weblogs with "mini-blogs" on the sidebar.

Entry

an Entry element is identified by class="entry"
an Entry element represents the concept of an atom entry
a weblog entry MUST be enclosed in a single Entry element

That's what it's for, after all.

an Entry MUST NOT belong to more than one Feed element

That is, an Entry belongs to 0 or 1 Feeds.

an Entry SHOULD have an enclosing Feed element

Entry Title

an Entry Title element is identified <h#> in block elements OR non-preferentially class="title" in inline elements
an Entry Title element represents the concept of an atom entry title

Disambiguation

the first hAtom valid <h#> element to appear in an hAtom document is the Entry Title
otherwise, the first hAtom valid non-<abbr> element with a class="title" is the Entry Title

hAtom valid meaning somewhere where we expect it (like not inside Entry Content, for example).

otherwise, the Entry Title is the empty string

Atom does not allow for an entry not to have a title.

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="summary"
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
the "logical Entry Summary" may differ in different copies of the Entry

There is the major difference with Entry Content. We can summarize an Entry in different way in different places with no requirement for consistency. There may be issues with this for modelers: if so, take it up in hatom-issues.

Entry Permalink

an Entry Permalink element is identified by rel="bookmark"

We recognize that we have broken from Atom terminology at this point. See hatom-issues for discussion.

This may be a microformat in itself: rel-bookmark.

an Entry Permalink element represents the concept of an atom link in an entry
Entry Permalinks MUST 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.

Is there a problem with FeedBurner?

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 are circumstances (should as media pages) where this won't happen. See the next rule.

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 class="published"
a Entry Published element represents the concept of an 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

Disambiguation

The first valid element in an Entry marked as an Entry Published is the Entry Published element

Entry Author

IN PROGRESS OF BEING WRITTEN

an Entry Author element is identified by class="author"
a Entry Author element represents the concept of an atom author

XMDP Profile

Parsing Details

Examples

This section is informative.

Transformation 1

A well behaved weblog.

Original:

<body>
 <div id="wrap">
  <div id="content">
   ...
   <div class="entry">
    <h3 id="post-60">
     <a href="http://www.microformats.org/blog/..." rel="bookmark" title="...">Wiki Attack</a>
    </h3>
    <p>We had a bit of trouble with ...</p>
    <p>We’ve restored the wiki and ...</p>
    <p>If anyone is working to combat said spammers ...</p>

    <h4 class="tags">Technorati Tags:</h4>
    <ul class="tags">
     <li><a href="http://technorati.com/tag/mediawiki" rel="tag">mediawiki</a></li>
     <li><a href="http://technorati.com/tag/microformats" rel="tag">microformats</a></li>
     <li><a href="http://technorati.com/tag/spam" rel="tag">spam</a></li>
    </ul>

    <ul class="post-info">
     <li>
      <a href="http://www.microformats.org/blog/..." rel="bookmark" title="...">October 10th, 2005</a>
     </li>
     <li>
      <address class="vcard"><a class="url fn" href="http://theryanking.com">Ryan King</a></address>
     </li>
     <li>
      <a href="http://www.microformats.org/blog/...">4 Comments</a>
     </li>
    </ul>
   </div>
   
   <div class="entry">
   ....
   </div>
   ...
  </div>
 </div>
</body>

Transformed to hAtom compliant (shown in UPPER CASE for visibility only):

<body>
 <div id="wrap">
  <div id="ATOMFEED content">
   ...
   <div class="ATOMENTRY entry" ID="post-60">
    <h3>
     <a href="http://www.microformats.org/blog/..." rel="bookmark" title="...">Wiki Attack</a>
    </h3>
    <DIV CLASS="CONTENT">
     <p>We had a bit of trouble with ...</p>
     <p>We’ve restored the wiki and ...</p>
     <p>If anyone is working to combat said spammers ...</p>
    </DIV>

    <h4 class="tags">Technorati Tags:</h4>
    <ul class="tags">
     <li><a href="http://technorati.com/tag/mediawiki" rel="tag">mediawiki</a></li>
     <li><a href="http://technorati.com/tag/microformats" rel="tag">microformats</a></li>
     <li><a href="http://technorati.com/tag/spam" rel="tag">spam</a></li>
    </ul>

    <ul class="post-info">
     <li>
      <a href="http://www.microformats.org/blog/..." rel="bookmark" 
        title="..."><ABBR CLASS="PUBLISHED" TITLE="20051010T14:07:00-0700">October 10th, 2005</ABBR></a>
     </li>
     <li>
      <address class="vcard"><a class="url fn" href="http://theryanking.com">Ryan King</a></address>
     </li>
     <li>
      <a href="http://www.microformats.org/blog/...">4 Comments</a>
     </li>
    </ul>
   </div>
   
   <div class="entry entry" ID="post-59">
   ....
   </div>
   ...
  </div>
 </div>
</body>

Changes:

Added class="feed" to Feed
Added class="entry" to each Entry
Moved id="###" from <h3> to Entry
Added <div class="content">...</div> around the Entry Content
Added <abbr class="PUBLISHED" title="YYYYMMDDThh:mm:ss+ZZZZ">...</abbr> around the Entry Datetime

Also note:

We did not need to add a <address> element
We did not need to add a <h#> element
We did not need to add a rel="link" to Entry Permalinks

Transformation 2

A not-so well behaved weblog (an older blogspot weblog)

Original:

<body bgcolor="...">

 <div class="posts">
  <a name="112993192128302715"> </a><br>
  <div style="clear:both;"></div><strong>Nelson's final prayer</strong> 
  written on the night before Trafalgar:<blockquote>May the Great God, ... heart.
  <div style="clear:both; padding-bottom: 0.25em;"></div>
  <br>
  <span class="byline">
   posted by Natalie at 
   <a href="2005_10_16_nataliesolent_archive.html#112993192128302715">9:49 PM</a>
  </span>
 </div>

 <div class="posts">
  <a name="112993022840118939"> </a>
  <br>
  <div style="clear:both;"></div><strong>I really, truly </strong>didn't go ... view.
  <div style="clear:both; padding-bottom: 0.25em;"></div>
  <br>
  <span class="byline">
   posted by Natalie at 
   <a href="2005_10_16_nataliesolent_archive.html#112993022840118939">9:28 PM</a>
  </span>
 </div>
 ...

</body>

Transformed to hAtom compliant (shown in UPPER CASE for visibility only):

<body bgcolor="...">

 <DIV CLASS="ATOMFEED">
  <div class="ATOMENTRY posts" ID="112993192128302715">
   <strong CLASS="TITLE CONTENT">
    Nelson's final prayer
   </strong> 
   <SPAN CLASS="CONTENT">
    written on the night before Trafalgar:<blockquote>May the Great God, ... heart.
   </SPAN>
   <DIV>
    <span class="byline">posted by <address>Natalie</address> at 
     <a REL="LINK" href="HTTP://NATALIESOLENT.BLOGSPOT.COM/2005_10_16_nataliesolent_archive.html#112993192128302715">
     <ABBR CLASS="POSTED" TITLE="20051024T094900-0000">9:49 PM</ABBR></a>
    </span>
   </DIV>
  </div>

  <div class="entry posts" ID="112993022840118939">
   <strong CLASS="TITLE CONTENT">I really, truly </strong>
   <SPAN CLASS="CONTENT">
    didn't go ... view.
   </SPAN>
   <DIV>
    <span class="byline">
     posted by <address>Natalie</address> at 
     <a REL="LINK" href="HTTP://NATALIESOLENT.BLOGSPOT.COM/2005_10_16_nataliesolent_archive.html#112993022840118939">
     <ABBR CLASS="POSTED" TITLE="20051024T094900-0000">9:28 PM</ABBR></a>
    </span>
   </DIV>
  </div>
 ...
 </DIV>

</body>

Changes:

Added class="feed" to Feed
Added class="entry" to each Entry
Moved id="###" up to the Entry (and deleted the empty anchor block)
Added rel="link" to the Entry Permalinks
Made the Entry Permalink non-relative
Added <span class="title">...</div> around the Entry Title
Added <span class="content">...</div> around the Entry Title (!)
Added <span class="content">...</div> around the Entry Content
Added <abbr class="posted" title="YYYYMMDDThh:mm:ss+ZZZZ">...</abbr> around the Entry Datetime
Added <address> to the poster's name

Also note:

there are multiple content blocks, because Natalie Solent embeds the title in the content
cleaned up lots of crap HTML presentation stuff, with the assumption it would be fixed in the stylesheet
this is one of the uglier transformations you're likely to see

Transformation 3

A media page.

Original:

Transformed to hAtom compliant:

Changes:

Transformation 4

A bulletin board (PunBB)

Original:

<body>
 <div id="punwrap">
  <div id="punviewtopic" class="pun">

   <div id="brdheader" class="block">
    ... header stuff ...
   </div>

   <div id="announce" class="block">
    ... announcement stuff ...
   </div>

   <div class="linkst">
    ... controls for the blog
   </div>

   <div id="p54390" class="blockpost rowodd firstpost">
    <h2>
     <span><span class="conr">#1 </span>
     <a href="viewtopic.php?pid=54390#p54390">2005-10-16 10:36:24</a></span>
    </h2>
    <div class="box">
     <div class="inbox">
      <div class="postleft">
       <dl>
        <dt><strong><a href="profile.php?id=2">Rickard</a></strong></dt>

        <dd class="usertitle"><strong>PunBB Developer</strong></dd>
        <dd class="postavatar"><img src="img/avatars/2.png" width="60" height="60" alt="" /></dd>
        <dd>From: 127.0.0.1</dd>
        <dd>Registered: 2001-11-02</dd>
        <dd>Posts: 7806</dd>
        <dd class="usercontacts"><a href="http://www.punbb.org/">Website</a></dd>

       </dl>
      </div>
      <div class="postright">
       <h3>PunBB 1.2.9</h3>
       <div class="postmsg">
        <p>Just a quick note this time....</p>

       </div>
       <div class="postsignature"><hr />"Programming is like sex: ...</div>
      </div>
      <div class="clearer"></div>
      <div class="postfootleft"><p>Offline</p></div>
      <div class="postfootright"><div> </div></div>
     </div>
    </div>

   </div>

   <div id="p54392" class="blockpost roweven">
    <h2><span><span class="conr">#2 </span><a href="viewtopic.php?pid=54392#p54392">2005-10-16 10:54:41</a></span></h2>
    <div class="box">
     <div class="inbox">
      <div class="postleft">
       <dl>
        <dt><strong><a href="profile.php?id=5298">IdleFire</a></strong></dt>

        <dd class="usertitle"><strong>Member</strong></dd>
        <dd class="postavatar"></dd>
        <dd>Registered: 2005-10-14</dd>
        <dd>Posts: 27</dd>
       </dl>
      </div>
      <div class="postright">

       <h3> Re: PunBB 1.2.9</h3>
       <div class="postmsg">
        <p>...</p>
       </div>
      </div>
      <div class="clearer"></div>
      <div class="postfootleft"><p>Offline</p></div>

      <div class="postfootright"><div> </div></div>
     </div>
    </div>
   </div>
   
   ... more entries ...

   <div id="brdfooter" class="block">
    ... footer stuff ...
   </div>

  </div>
 </div>
</body>

Transformed to hAtom compliant (changes shown in UPPER CASE for visibility only):

<body>
 <div id="punwrap">
  <div id="punviewtopic" class="pun">

   <div id="brdheader" class="block">
    ... header stuff ...
   </div>

   <div id="announce" class="block">
    ... announcement stuff ...
   </div>

   <div class="linkst">
    ... controls for the blog
   </div>

   <div id="p54390" class="ATOMENTRY blockpost rowodd firstpost">
    <h2>
     <span><span class="conr">#1 </span>
     <a REL="BOOKMARK" href="HTTP://FORUMS.PUNBB.ORG/viewtopic.php?pid=54390#p54390">
      <ABBR CLASS="POSTED" TITLE="20051016T103624-0500">2005-10-16 10:36:24</ABBR>
     </a></span>
    </h2>
    <div class="box">
     <div class="inbox">
      <div class="postleft">
       <dl>
        <dt><strong><ADDRESS><a href="profile.php?id=2">Rickard</a></ADDRESS></strong></dt>

        <dd class="usertitle"><strong>PunBB Developer</strong></dd>
        <dd class="postavatar"><img src="img/avatars/2.png" width="60" height="60" alt="" /></dd>
        <dd>From: 127.0.0.1</dd>
        <dd>Registered: 2001-11-02</dd>
        <dd>Posts: 7806</dd>
        <dd class="usercontacts"><a href="http://www.punbb.org/">Website</a></dd>

       </dl>
      </div>
      <div class="postright">
       <h3>PunBB 1.2.9</h3>
       <div class="CONTENT postmsg">
        <p>Just a quick note this time....</p>

       </div>
       <div class="postsignature"><hr />"Programming is like sex: ...</div>
      </div>
      <div class="clearer"></div>
      <div class="postfootleft"><p>Offline</p></div>
      <div class="postfootright"><div> </div></div>
     </div>
    </div>

   </div>

   <div id="p54392" class="ATOMENTRY blockpost roweven">
    <h2>
     <span><span class="conr">#2 </span>
     <a REL="BOOKMARK" href="HTTP://FORUMS.PUNBB.ORG/viewtopic.php?pid=54392#p54392">
      <ABBR CLASS="POSTED" TITLE="20051016T1105441-0500">2005-10-16 10:54:41</ABBR>
     </a></span>
    </h2>
    <div class="box">
     <div class="inbox">
      <div class="postleft">
       <dl>
        <dt><strong><ADDRESS><a href="profile.php?id=5298">IdleFire</a></ADDRESS></strong></dt>

        <dd class="usertitle"><strong>Member</strong></dd>
        <dd class="postavatar"></dd>
        <dd>Registered: 2005-10-14</dd>
        <dd>Posts: 27</dd>
       </dl>
      </div>
      <div class="postright">

       <h3> Re: PunBB 1.2.9</h3>
       <div class="CONTENT postmsg">
        <p>...</p>
       </div>
      </div>
      <div class="clearer"></div>
      <div class="postfootleft"><p>Offline</p></div>

      <div class="postfootright"><div> </div></div>
     </div>
    </div>
   </div>
   
   ... more entries ...

   <div id="brdfooter" class="block">
    ... footer stuff ...
   </div>

  </div>
 </div>
</body>

Changes:

Notes:

Questions:

should the address enclose the entire author block?

More 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

Semantically-Interlinked Online Communities (SIOC) RDF Ontology

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:

blog-post Brainstorming

Discussions

See blogs discussing this page.

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.

hatom

hAtom

Draft Specification

Editor

Authors

Copyright

Patents

Introduction

Semantic XHTML Design Principles

Format

In General

Schema

Nomenclature

Nesting Rules

hAtom Opaque

Cardinality

Logical Cardinality

Rules and Definitions

Feed

Entry

Entry Title

Disambiguation

Entry Content

Entry Summary

Entry Permalink

Disambiguation

Entry Published

Disambiguation

Entry Author

XMDP Profile

Parsing Details

Examples

Transformation 1

Transformation 2

Transformation 3

Transformation 4

More Examples

Examples in the wild

Implementations

References

Normative References

Informative References

Specifications That Use hAtom

Similar Work

Work in progress

Discussions

Q&A

Issues

See Also

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