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re: Microdata: itemid attribute (feedback)

From: John Giannandrea <jg@metaweb.com>
Date: Sun, 25 Oct 2009 00:28:51 -0700
Message-Id: <E20D342A-D838-46B0-BBB0-9205EB86E125@metaweb.com>
To: public-html@w3.org

Martin McEvoy wrote:
 > I am unsure if itemid has any actual practical use (either that of  
I am
 > misunderstanding something).
 > Itemid is used as a global Identifier for an Item, its value must be
 > valid absolute url, what I am unsure of is how to actually use this?

One important use case for itemid is when a page wants to identify  
some web resource only a subset of whoes data is on the page markup.

For example imagine a page displaying a TV show, and links to the  
previous and next episode names, and when you click on them the JS in  
the page is able to request more data from a web service and update  
the DOM in place.    To do this it needs some token that represents  
the next episode, which would be the itemid.

While you can argue that this identifier could be application and web  
service specific there is precedent from RDF that the thing being  
referred to in the markup should be a URI uniquely naming the thing.

There is a larger point which is that much HTML today is a rendition  
of data which lives in databases, often with well known keys for the  
primary record (like ISBN numbers, or BBC program ids).   Allowing an  
author to optionally emit these IDs on the page in some standard way  
makes the web more interoperable at a semantic level, as well as  
providing immediate practical benefits.

A second use case is for search engines, which would benefit from  
being told what real world entities the HTML claims to describe.  If  
you look at a product like google squared, or bing visual search it  
would seem very likely that they would benefit from itemids and  
itemprops at almost any level of convergence.

-jg
http://freebase.com
Received on Sunday, 25 October 2009 07:30:00 UTC

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