[uf-dev] Specification of Value-Excerpting

Ben Ward lists at ben-ward.co.uk
Thu May 22 07:08:30 PDT 2008

Related to the machine-data documentation and empty-element-value- 
excerpting http://microformats.org/wiki/machine-data, I'd like to get  
proper documentation written on the value-excerpting behaviour first  
described in hCard.

It's currently covered by a single paragraph in the hCard spec, which  
is massively insufficient. It's also exposed issues lately about  
putting values out of nested microformats and even just out of  
complexly nested properties.

I'm vaguely aware that Operator has implemented safety nets by not  
parsing with other known microformats, but that seems to be flawed  
solution as it depends on every parser knowing about every other  
microformat. There's the ongoing class=mfo idea, which is a separate  
solution to that problem, but we should get the parsing behaviour of  
class=value (sans mfo) tightened up.

I've created an initial wiki page at <http://microformats.org/wiki/value-excerption-pattern 
 > — with basic starting points of how it's supposed to work. However,  
I don't understand the intricacies of existing implementations enough  
to fully document parsing, so it's marked as being a ‘draft, don't  
publish this yet’ page.

One requirement for value-excerption that seems critical is that it  
must be implementable without parsers having knowledge of every other  
microformat. It needs to be possible to write an ‘hcard parser’ that  
stands alone, nor that needs to be updated every time a new  
microformat is developed.

There are some other notes on that page too, and a ‘parsing to-do’  
list that I'd encourage you all to add to, so that we can get this  
fully defined and interoperable.

Thanks and regards,


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