include-pattern

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<h1> include pattern </h1>
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<h1>Include Pattern</h1>
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{{TOC-right}}
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The include pattern is a microformat design pattern, providing a mechanism to include a portion of data from one area of a page into another area of the same page, allowing the data to be reused by multiple microformats, independent of content order, without repeating all the information. The following is documentation for re-use of the pattern in other microformats, and for publishers working with it.
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Initially developed as part of [[resume-brainstorming]], it has become clear from actual microformats markup experience with real world sites, that several microformats (e.g. [[hresume|hResume]], [[hreview|hReview]], [[hatom|hAtom]] etc.) need a mechanism to include a portion of data from area of a page into another area of a page.  This page documents this pattern for re-use in those microformats and any others that need this feature.
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;Editors: Tantek Çelik
 +
: Ben Ward
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; Author: Tantek Çelik
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== background ==
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__TOC__
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[[hresume|hResume]] needed the ability to include a name from one hCard at the top of a resume — the person's contact details — into the separate hCards used in the same person's employment history. Repeating name information would not have matched the existing publishing practices used in Resumes and Curriculum Vitæ, would be inconvenient to publishers, and irritating to consumers. The include pattern is a mechanism to reference data from the same page, avoiding repetition, or duplicate visible information.
 +
== scope ==
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== background ==
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The include pattern is strictly limited to the scope of the current page. It cannot be used to include content from other URLs.
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In [[hresume|hResume]], we needed the ability to include the name from the hCard at the top of the resume for a person into their hCards in the middle of the resume which represented each of their job hCards (job title, organization name, address etc.), and thus developed the [http://microformats.org/wiki/resume-brainstorming#hCard_reference_via_object hCard reference via object technique].
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== quick reference==
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== scope ==
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The include-pattern is a mechanism to include content from one microformat into another microformat elsewhere in the same document, using hyperlinks or <code>object</code>. For example:
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The include pattern is strictly limited to the scope of the current page.  This is by design in order to avoid multipage / multidomain etc. problems.  Also "current page" uses cover the vast majority of use cases thus we are solving that problem first.
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<source lang=html4strict><a class="include" href="#author">James Levine</a></source>
 +
<source lang=html4strict><object class="include" data="#author"></object></source>
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== class name "include" ==
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In specifications which cite the include-pattern, either of the above code snippets {{must}} cause a microformats parser to replace the <code>A</code> or <code>object</code> element with class name "include" with the content fragment with ID "author". Full examples follow.
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In order to make this more explicit (helps forward compatibility for parsers), we are adding the class name "include" on the object element to indicate that that object refers to a subtree which should be included in its place by microformat parsers.
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== in general==
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'''Proposal 1:''' Allow the use of <nowiki><a href class="include"></nowiki> as a secondary include-pattern mechanism, due to some browsers mishandling the object include-pattern.  See [[include-pattern-feedback]] for details.
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To reference includes, use an include element with class name "include" and a document fragment identifier. The content to be included should have an ID attribute set, and that ID should be referenced from the HREF or DATA attribute at the point of inclusion.
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== object include example ==
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The include element with class name "include" indicates a reference to a sub-tree elsewhere in the document which {{must}} be included in-place by microformat parsers. That is, the element with class "include" is _replaced_ in the DOM by the referenced sub-tree. Note that this means all other class names on the include element are discarded. Microformat class names should be included on the target of the include, not on the include element itself.
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Here is an example of an [[hcard|hCard]] you could have at the top of a page, shown here also as a verbose hCard for purposes of illustration that the reference may be to a subtree, not just a text node:
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To prevent infinite loops, if a class="include" refers to itself or to an ancestor in the parse tree, then it is ignored and has no effect on the parser.
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<pre><nowiki>
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Per the [[include-pattern#Scope|scope]], the <code>object</code> 'data' attribute and hyperlink 'href' attribute {{must}} be local ID references when used as include pattern instances. External references (requiring a consuming application to load an external resource) are not supported by this method.
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<span class="vcard">
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<span class="fn n" id="j">
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  <span class="given-name">James</span> <span class="family-name">Levine</span>
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</span>
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</span>
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</nowiki></pre>  
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-
Somewhere else on the page, you could have another hCard which would re-use that "fn n" content from the first hCard:
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There are two HTML elements available to reference includes, hyperlink/Anchor and <code>object</code>. They are documented below.
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<pre><nowiki>
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These methods of property indirection via a hyperlink element can apply to any/all properties in class-based microformats, but should only be used where a microformat explicitly states that the include-pattern is a dependency. For example, [[XOXO]] does not reference the include-pattern at this time, so sub-trees cannot be included by reference in XOXO. [[hResume]] and [[hReview]] do reference the include pattern.
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<span class="vcard">
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<object data="#j" class="include"></object>
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<span class="org">SimplyHired</span>
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<span class="title">Microformat Brainstormer</span>
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</span>
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</nowiki></pre>
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-
Thus a microformat parser would treat the above as follows, with the object include completely replaced by the subtree that it references:
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=== Hyperlink ===
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<pre><nowiki>
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The recommended way to reference includes within microformats is to use a hyperlink.
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<span class="vcard">
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-
<span class="fn n" id="j">
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  <span class="given-name">James</span> <span class="family-name">Levine</span>
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</span>
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<span class="org">SimplyHired</span>
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<span class="title">Microformat Brainstormer</span>
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</span>
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</nowiki></pre>
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-
This method of hCard property indirection via an object element can apply to any/all properties in class-based microformats.
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==== Hyperlink example====
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Note 1: '''the object data attribute MUST be a local ID reference.'''  External references (which would require a consuming application to load an external resource) are currently not supported by this method.
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Here is an [[hcard|hCard]] for a bar, included at the top of a reviews page, shown here as a verbose hCard.
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Note 2: To avoid unsightly messes in Safari, you should include the following style rule in a style sheet for the page:
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<source lang=html4strict>
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<pre><nowiki>
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<div class="vcard" id="bricklayers-card">
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object.include { width:0; height:0 }
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  <div class="fn org">The Bricklayers Arms</div>
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</nowiki></pre>
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  <div class="adr">
 +
    <span class="street-address">31 Gresse Street</span>,
 +
    <span class="locality">Fitzrovia</span>
 +
    <span class="region">London</span>
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    <span class="postal-code">W1T 1QS</span>
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  </div>
 +
</div>
 +
</source>
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Note 3: To prevent infinite loops, if a class="include" refers to itself or an ancestor in the parse tree, then it is ignored and has no effect on the parser.
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Elsewhere on the page, a number of reviews reference the hcard in the item property. Rather than repeat all the verbose detail, only the name is reprinted and the detailed hcard referenced using the include-pattern.
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== hyperlink include example ==
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<source lang=html4strict>
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<div class="hreview">
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  <h1 class="summary">A great venue for monthly gatherings!</h1>
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  <div class="item"><a class="include" href="#bricklayers-card">The Bricklayers Arms</a></div>
 +
  <p class="description">Wonderful pub, cheap beer, open fire to warm mince pies at Christmas.</p>
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</div>
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Per the proposal 1 above, here is how you would code the above object include example using the <nowiki><a href></nowiki> tag.
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<div class="hreview">
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  <h1 class="summary">Takes a while to thin out, but!</h1>
 +
  <div class="item"><a class="include" href="#bricklayers-card">The Bricklayers Arms</a></div>
 +
  <p class="rating"><span class="value">5</span>/<span class="best">5</span></p>
 +
</div>
 +
</source>  
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<pre><nowiki>
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Note that you {{must}} include content within the anchor element. See the notes and issues below.
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<span class="vcard">
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<a href="#j" class="include"></a>
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A microformat parser {{must}} treat each review as follows, with the hyperlink include element completely replaced (including inner-text) by the sub-tree that was referenced:
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<span class="org">SimplyHired</span>
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<span class="title">Microformat Brainstormer</span>
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<source lang=html4strict>
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</span>
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<div class="hreview">
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</nowiki></pre>  
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  <h1 class="summary">A great venue for monthly gatherings!</h1>
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  <div class="item">
 +
      <div class="vcard" id="bricklayers-card">
 +
        <div class="fn org">The Bricklayers Arms</div>
 +
        <div class="adr">
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          <span class="street-address">31 Gresse Street</span>,
 +
          <span class="locality">Fitzrovia</span>
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          <span class="region">London</span>
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          <span class="postal-code">W1T 1QS</span>
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        </div>
 +
      </div>
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  </div>
 +
  <p class="description">Wonderful pub, cheap beer, open fire to warm mince pies at Christmas.</p>
 +
</div>
 +
 
 +
</source>
 +
 
 +
==== notes and issues ====
 +
 
 +
Note: The <code>id</code> attribute value in the example "bricklayers-card" was chosen for demonstration purposes. The text of the value has no semantic per the include-pattern other than to connect the source of the include to the destination. Authors {{should}} use good [[POSH]] techniques to choose <code>id</code> and <code>class</code> names.
 +
 
 +
Authors {{must}} supply content text for the hyperlink itself. This can require repeating a small piece of information (such as a person's name in an hcard), or including generic text as appropriate to the context of the page.
 +
 
 +
===== accessibility =====
 +
 
 +
* Testing indicates that the only way to guarantee accessibility of hyperlinks to users of assistive technology (such as screen readers) is to include inner-text. [http://yuiblog.com/blog/2008/01/23/empty-links/ See: Empty Links and Screen Readers]
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* You {{must}} include inner-text in the hyperlink element.
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* You MAY enhance the rendered user experience (depending on the context of your page) by hiding the include element using CSS <code>display: none</code>
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* Where you wish to hide the content of the include element, you {{should not}} hide the include element using a CSS negative margin offset as the hidden link will remain in the tab order of the document. Use <code>display: none</code> instead.
 +
 
 +
Where a publishing constraint prevents putting content within the include-pattern, you {{must}} use the <code>object</code> element pattern instead of a hyperlink.
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 +
=== Object ===
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Changes:
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The Object Include Pattern is semantically superior to the Hyperlink Include; it is being used to embed content into the page. The <code>object</code> element based include was the original developed include pattern. However, there are some browser compatibility issues that can affect some implementation scenarios and thus the above Hyperlink Include Pattern is preferred.
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# a open/close tag instead of object open/close tag
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# href attribute instead of data attribute
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# ... that's it.  only 2 changes.  
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==== Object example ====
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And just as in the object include example, the end effective result to the parser is the same, and the same '''Notes''' apply.
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The [[hcard|hCard]] from the beginning of a resumé describes the person who's resumé it is:
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<pre><nowiki>
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<source lang=html4strict>
<span class="vcard">
<span class="vcard">
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<span class="fn n" id="j">
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  <span class="fn n" id="james-hcard-name">
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  <span class="given-name">James</span> <span class="family-name">Levine</span>
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    <span class="given-name">James</span> <span class="family-name">Levine</span>
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</span>
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  </span>
 +
</span>
 +
</source>
 +
 
 +
Elsewhere on the page, a second hCard, with employer information, re-uses the "fn n" content from the first hCard:
 +
 
 +
<source lang=html4strict>
 +
<span class="vcard">
 +
<object class="include" data="#james-hcard-name"></object>
  <span class="org">SimplyHired</span>
  <span class="org">SimplyHired</span>
  <span class="title">Microformat Brainstormer</span>
  <span class="title">Microformat Brainstormer</span>
</span>
</span>
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</nowiki></pre>  
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</source>  
 +
 
 +
A microformat parser {{must}} treat the second hCard as follows, with the <code>object</code> include element completely replaced by the sub-tree that it referenced:
 +
 
 +
<source lang=html4strict>
 +
<span class="vcard">
 +
  <span class="fn n" id="james-hcard-name">
 +
    <span class="given-name">James</span> <span class="family-name">Levine</span>
 +
  </span>
 +
  <span class="org">SimplyHired</span>
 +
  <span class="title">Microformat Brainstormer</span>
 +
</span>
 +
</source>
 +
 
 +
This method of hCard property indirection via an object element can apply to any/all properties in class-based microformats.
 +
 
 +
=== notes and issues===
 +
 
 +
* Unlike the hyperlink pattern, the <code>object</code> is not believed to cause problems in assistive technology when fallback text is absent. ('''research needed''')
 +
* Apple's Safari 1.x browser has some rendering issues with this use of <code>object</code>: Publishers {{should}} style a width and height of "0" for the include elements to resolve this ('''clarification of issue needed''').
 +
* Bugs have been reported in some web browsers (Internet Explorer, Safari, Firefox) that <code>object</code> elements referencing fragments of the same document erroneously cause the browser to make additional HTTP requests ('''version(s) affected needed'''). For scenarios where HTTP requests are a performance issue, publishers {{should}} use the hyperlink pattern instead.
 +
* Versions of Microsoft Internet Explorer with ActiveX controls disabled will throw a warning prompt upon finding an <code>object</code> element ('''version(s) affected needed''').
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== Acknowledgments ==
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== acknowledgements ==
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Thanks to discussions and brainstorms with a bunch of folks: Ryan King, James Levine, the whole crowd at the [http://mashupcamp.com/index.cgi?HAtomFinalization Microformats specifications working session] at MashupCamp, Brian Suda, Scott Reynen, Drew McLellan.
+
Thanks to discussions and brainstorms with a bunch of folks: [http://theryanking.com/ Ryan King], James Levine, the whole crowd at the [http://mashupcamp.com/index.cgi?HAtomFinalization Microformats specifications working session] at MashupCamp, [http://suda.co.uk/ Brian Suda], [http://randomchaos.com/ Scott Reynen], [http://allinthehead.com/ Drew McLellan]. Thanks to [http://www.isolani.co.uk/ Mike Davies] for accessibility research.
-
== Specifications Using ==
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== specifications using ==
* [[hresume|hResume]]
* [[hresume|hResume]]
* [[hreview|hReview]]
* [[hreview|hReview]]
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=== Considering ===
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=== considering ===
 +
All class-based microformats {{should}} consider using and explicitly normatively stating support for the include pattern.
* [[hatom|hAtom]]
* [[hatom|hAtom]]
* [[hcalendar|hCalendar]]
* [[hcalendar|hCalendar]]
* [[hcard|hCard]]
* [[hcard|hCard]]
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* [[currency]]
 
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* [[measure]]
 
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== Implementations ==
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== implementations ==
* X2V implements the [[include-pattern]] when parsing [[hcard|hCards]] and [[hcalendar|hCalendars]] for both object.include and a.include.
* X2V implements the [[include-pattern]] when parsing [[hcard|hCards]] and [[hcalendar|hCalendars]] for both object.include and a.include.
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== References ==
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== references ==
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=== Normative ===
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=== normative ===
* HTML 4.01
* HTML 4.01
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* XHTML 1.0
 
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=== Informative ===
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=== informative ===
* [[hcard|hCard]]
* [[hcard|hCard]]
 +
* [[hresume|hResume]]
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* XHTML 1.0
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=== Related ===
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== related pages==
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{{include-pattern-related-pages}}
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* [http://www.mnot.net/javascript/hinclude.html Introducing HInclude] by Mark Nottingham.
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** HInclude is a markup extension + javascript library for including *external* files into an XHTML document.
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== Discussions ==
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* Feedback is encouraged on the [[include-pattern-feedback]] page.
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* See also [http://www.technorati.com/cosmos/referer.html blogs discussing this page].
* See also [http://www.technorati.com/cosmos/referer.html blogs discussing this page].
-
 
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=== Q&A ===
 
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* If you have any questions about include-pattern, check the [[include-pattern-faq|include-pattern FAQ]], and if you don't find answers, add your questions to the end of the page!
 
-
 
-
=== Issues ===
 
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* Please add any issues with the specification to the separate [[include-pattern-issues|include-pattern issues]] document.
 

Current revision

Include Pattern

Contents

The include pattern is a microformat design pattern, providing a mechanism to include a portion of data from one area of a page into another area of the same page, allowing the data to be reused by multiple microformats, independent of content order, without repeating all the information. The following is documentation for re-use of the pattern in other microformats, and for publishers working with it.

Editors
Tantek Çelik
Ben Ward

background

hResume needed the ability to include a name from one hCard at the top of a resume — the person's contact details — into the separate hCards used in the same person's employment history. Repeating name information would not have matched the existing publishing practices used in Resumes and Curriculum Vitæ, would be inconvenient to publishers, and irritating to consumers. The include pattern is a mechanism to reference data from the same page, avoiding repetition, or duplicate visible information.

scope

The include pattern is strictly limited to the scope of the current page. It cannot be used to include content from other URLs.

quick reference

The include-pattern is a mechanism to include content from one microformat into another microformat elsewhere in the same document, using hyperlinks or object. For example:

<a class="include" href="#author">James Levine</a>
<object class="include" data="#author"></object>

In specifications which cite the include-pattern, either of the above code snippets MUST cause a microformats parser to replace the A or object element with class name "include" with the content fragment with ID "author". Full examples follow.

in general

To reference includes, use an include element with class name "include" and a document fragment identifier. The content to be included should have an ID attribute set, and that ID should be referenced from the HREF or DATA attribute at the point of inclusion.

The include element with class name "include" indicates a reference to a sub-tree elsewhere in the document which MUST be included in-place by microformat parsers. That is, the element with class "include" is _replaced_ in the DOM by the referenced sub-tree. Note that this means all other class names on the include element are discarded. Microformat class names should be included on the target of the include, not on the include element itself.

To prevent infinite loops, if a class="include" refers to itself or to an ancestor in the parse tree, then it is ignored and has no effect on the parser.

Per the scope, the object 'data' attribute and hyperlink 'href' attribute MUST be local ID references when used as include pattern instances. External references (requiring a consuming application to load an external resource) are not supported by this method.

There are two HTML elements available to reference includes, hyperlink/Anchor and object. They are documented below.

These methods of property indirection via a hyperlink element can apply to any/all properties in class-based microformats, but should only be used where a microformat explicitly states that the include-pattern is a dependency. For example, XOXO does not reference the include-pattern at this time, so sub-trees cannot be included by reference in XOXO. hResume and hReview do reference the include pattern.

Hyperlink

The recommended way to reference includes within microformats is to use a hyperlink.

Hyperlink example

Here is an hCard for a bar, included at the top of a reviews page, shown here as a verbose hCard.

<div class="vcard" id="bricklayers-card">
  <div class="fn org">The Bricklayers Arms</div>
  <div class="adr">
     <span class="street-address">31 Gresse Street</span>,
     <span class="locality">Fitzrovia</span>
     <span class="region">London</span>
     <span class="postal-code">W1T 1QS</span>
  </div>
</div>

Elsewhere on the page, a number of reviews reference the hcard in the item property. Rather than repeat all the verbose detail, only the name is reprinted and the detailed hcard referenced using the include-pattern.

<div class="hreview">
   <h1 class="summary">A great venue for monthly gatherings!</h1>
   <div class="item"><a class="include" href="#bricklayers-card">The Bricklayers Arms</a></div>
   <p class="description">Wonderful pub, cheap beer, open fire to warm mince pies at Christmas.</p>
</div>
 
<div class="hreview">
   <h1 class="summary">Takes a while to thin out, but!</h1>
   <div class="item"><a class="include" href="#bricklayers-card">The Bricklayers Arms</a></div>
   <p class="rating"><span class="value">5</span>/<span class="best">5</span></p>
</div>

Note that you MUST include content within the anchor element. See the notes and issues below.

A microformat parser MUST treat each review as follows, with the hyperlink include element completely replaced (including inner-text) by the sub-tree that was referenced:

<div class="hreview">
   <h1 class="summary">A great venue for monthly gatherings!</h1>
   <div class="item">
      <div class="vcard" id="bricklayers-card">
        <div class="fn org">The Bricklayers Arms</div>
        <div class="adr">
           <span class="street-address">31 Gresse Street</span>,
           <span class="locality">Fitzrovia</span>
           <span class="region">London</span>
           <span class="postal-code">W1T 1QS</span>
        </div>
      </div>
   </div>
   <p class="description">Wonderful pub, cheap beer, open fire to warm mince pies at Christmas.</p>
</div>

notes and issues

Note: The id attribute value in the example "bricklayers-card" was chosen for demonstration purposes. The text of the value has no semantic per the include-pattern other than to connect the source of the include to the destination. Authors SHOULD use good POSH techniques to choose id and class names.

Authors MUST supply content text for the hyperlink itself. This can require repeating a small piece of information (such as a person's name in an hcard), or including generic text as appropriate to the context of the page.

accessibility

Where a publishing constraint prevents putting content within the include-pattern, you MUST use the object element pattern instead of a hyperlink.

Object

The Object Include Pattern is semantically superior to the Hyperlink Include; it is being used to embed content into the page. The object element based include was the original developed include pattern. However, there are some browser compatibility issues that can affect some implementation scenarios and thus the above Hyperlink Include Pattern is preferred.

Object example

The hCard from the beginning of a resumé describes the person who's resumé it is:

<span class="vcard">
  <span class="fn n" id="james-hcard-name">
    <span class="given-name">James</span> <span class="family-name">Levine</span>
  </span>
</span>

Elsewhere on the page, a second hCard, with employer information, re-uses the "fn n" content from the first hCard:

<span class="vcard">
 <object class="include" data="#james-hcard-name"></object>
 <span class="org">SimplyHired</span>
 <span class="title">Microformat Brainstormer</span>
</span>

A microformat parser MUST treat the second hCard as follows, with the object include element completely replaced by the sub-tree that it referenced:

<span class="vcard">
  <span class="fn n" id="james-hcard-name">
    <span class="given-name">James</span> <span class="family-name">Levine</span>
  </span>
  <span class="org">SimplyHired</span>
  <span class="title">Microformat Brainstormer</span>
</span>

This method of hCard property indirection via an object element can apply to any/all properties in class-based microformats.

notes and issues

acknowledgements

Thanks to discussions and brainstorms with a bunch of folks: Ryan King, James Levine, the whole crowd at the Microformats specifications working session at MashupCamp, Brian Suda, Scott Reynen, Drew McLellan. Thanks to Mike Davies for accessibility research.

specifications using

considering

All class-based microformats SHOULD consider using and explicitly normatively stating support for the include pattern.

implementations

references

normative

informative

related pages

include-pattern was last modified: Sunday, April 7th, 2013

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