What is the HTML5 itemid attribute and how do you use it?

Can someone give me a couple of examples on how to code the itemid attribute开发者_运维技巧 for HTML5 as well as what the itemid attribute is used for?

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It's a global identifier for a Microdata item. If you're not using Microdata you shouldn't need itemid for anything, if you are using Microdata you should review the many examples in the spec. If the spec is too dense for you, here's some tutorials:

• Microdata: HTML5’s Best-Kept Secret
• HTML5 Microdata: Welcome to the Machine
• Dive into HTML5: Distributed Extensibility

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I also has the same problem. Wherever I read, I found that confusing. Here is just one paragraph which is clear with example. http://www.w3.org/TR/2011/WD-microdata-20110405/#global-identifiers-for-items