According to schema.org, this is how you are supposed to mark up your html to make use of "rich snippet" metadata that is to be gobbled up by search engines:
<div itemscope itemtype="http://schema.org/Event">
But itemscope on itself is invalid. It's a boolean value, not an attribute like itemscope="true"
I'm using PHPTAL and it refuses to process my page once it runs into this attribute. Other validators choke as well.
So is schema.org's specification just plain wrong?
It is a boolean attribute, which is perfectly acceptable in HTML5.
I expect that your parsers are just old. The W3C validation service has no issues with schema.org's formats.
Added linky: http://www.w3.org/TR/html5/common-microsyntaxes.html#boolean-attribute
Just to update this for posterity, the answer is to fully qualify boolean properties. This means using a syntax like itemscope="itemscope"