**Microdata** [extends](http://www.w3.org/TR/2013/NOTE-microdata-20131029/#content-models) HTML5 in a way that `link` and `meta` elements can be used in the `body`, **if** they contain an `itemprop` attribute. 

> If the `itemprop` attribute is present on `link` or `meta`, they are flow content and phrasing content. The `link` and `meta` elements may be used where phrasing content is expected if the `itemprop` attribute is present.

This extension is currently also included in the HTML 5.1 Nightly (Editor’s Draft)  (see [`link` element](http://www.w3.org/html/wg/drafts/html/master/document-metadata.html#the-link-element) and [`meta` element](http://www.w3.org/html/wg/drafts/html/master/document-metadata.html#the-meta-element)). But as the [Microdata specification became a W3C Note](http://www.w3.org/TR/2013/NOTE-microdata-20131029/) recently, we’ll have to see what happens with this reference.

**RDFa 1.1** [extends](http://www.w3.org/TR/2013/REC-html-rdfa-20130822/#extensions-to-the-html5-syntax) HTML5 in a way that `link` and `meta` elements can be used in the `body`, if they contain a `propertỳ` attribute.

> If the `@property` RDFa attribute is present on the `link` or `meta` elements, they MUST be viewed as conforming if used in the `body` of the document. More specifically, when `link` or `meta` elements contain the RDFa `@property` attribute and are used in the `body` of an HTML5 document, they MUST be considered flow content.

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So you are **not** allowed to use *any* `link` element (e.g., `<link href="" rel="" />`) in the `body`, but only those with an `itemprop` attribute (for Microdata) resp. a `property` attribute (for RDFa).