value-class-pattern-brainstorming

value excerption pattern brainstorming

The value-excerption-pattern is derived from value-excerpting in hCard. The precise parsing behavior is not yet finalized, so the pattern should be used only with extreme caution.

This brainstorming page is for exploring ideas related to specifying the value-excerption-pattern in more detail and ideas for special case handling of the value-excerption-pattern in combination with specific semantic HTML elements per those elements' particular semantics.

These are merely explorations for now, and should NOT be used in actual content publishing, nor implemented in any production code.

Editor

Tantek Çelik

object param handling

2008-08-23 Ben Ward and Tantek Çelik brainstormed the following possible special case markup handling for the use of the value-excerption-pattern with the <object> element. Modified 2008-08-26.

The following markup example documents one way the hCard tel property's type subproperty could be specified with the enumerated value of "cell" while providing the UK English "mobile" as the human visible object text contents:

<object class="type" lang="en-GB">
 <param name="value" value="cell" />
 mobile
</object>

summary

• object element special case handling of value excerption. When a microformat (sub)property class name is specified on an object element, then value excerption handling is modified as follows:
• first param with name attribute value. if the first child of the object is a param element, and that param element has name attribute value of "value", then use the value attribute value for the value for the microformat (sub)property class name specified on the object.
• continue. if not, continue with existing value excerption handling, and microformat (sub)property parsing rules as currently best specified by hcard-parsing.

notes

Note that the param element does not have a 'class' attribute and thus its 'name' attribute (which has a compatible semantic) is used instead to invoke the value excerption pattern.

advantages

• Greater semantic re-use. The use of the param element to specify a value for its object is in line with the param element's semantics. The semantic association between the object and the param element is defined in the HTML4 specification.
• Less invention. This use of object param is superior to the use of a nested empty span element. The association of an empty span with its parent is a new semantic not previously defined in the HTML4 specification. Thus this use of object param markup better follows the principle of minimum invention as compared to nested empty span markup.

neutral

• Similar violation of DRY to nested empty span.

disadvantages

• Less human visible than abbr DRY violation. The contents/values of param elements are not exposed to the user of a browser, unlike the title attribute of abbr which, since it is commonly available as a hover tooltip, is more human visible, thus verifiable, than param.
• DRY violation content divergence risk greater than abbr. With abbr, one element is used to express both a human visible string and the property value, thus tying these values closer together (thus reducing risk of divergence). With object param, two elements are used, and thus risk of divergence may be greater than the use of abbr. Possible mitigating techniques that would help keep the property value and the equivalent human visible string closer to each other, perhaps as close in the code as they are when using abbr:
  1. require param be first child of object
  2. require use of only one param child (allow other child elements)
  3. require exclusive use of object for value excerption i.e. no using the same object for an actual replaced object and a value excerption
  4. require "value" attribute be the last attribute specified on the param element
  5. require equivalent human visible text be placed immediately (allowing for whitespace) following the param

to do

• Browser testing. This code sample must be tested in various browsers to determine how they process and handle pages with such code
  1. determine which browsers to test (based on popularity, deployment, etc.)
  2. write a full sample test case using the above object param markup pattern and a complete hCard
  3. write a more complex sample test case with multiple uses of the object param markup pattern
  4. test do browsers properly display the UK English text "mobile"?
  5. test do browsers generate multiple browser (e.g. Webkit, Trident etc.) controls as they would for embedded frames (nested HTML objects)?
  6. determine any other tests
• Parser implementability. Determine approximately how much work it would be to implement this special case object param support.
  • I've just added support for this. It took 19 bytes of code. TobyInk 01:24, 25 Aug 2008 (PDT)
• Document in more detail. Assuming browser tests of a simple example pass (proper visible text displayed, page efficiency not compromised by additional control creation), document how to handle/parse this pattern in more detail. Iterate.

previous iterations

20080823

<object class="type" lang="en-GB">
 <param class="value" name="value" value="cell" />
 mobile
</object>

disadvantages

• Invalid (X)HTML - although this pattern does make sense, it is worth noting that <param> is one of just a handful of HTML elements for which the class attribute is not defined. Use of this pattern will break validation unless a custom DTD is employed.

related pages

• value-excerption-pattern
• value-excerption-pattern-issues
• hCard: Value Excepting