The Schema.org method of building the Semantic Web relies on adding new terms to the existing HTML markup. For instance, you might add a description to the header tags, or even to the entire DIV.
The itemscope element is added to an HTML DIV to indicate to the search engine spiders that the current section is about a specific subject. In conjunction with this, Schema.org’s standard requires that an itemtype is also added; the content might be about a movie, for instance, so this will be indicated.
Certain items such as names are occasionally not recognized as such in HTML, so the itemprop element is used to add information to them, perhaps using the span tag. Other items might have multiple qualifications, with the result that further use of the itemscope and itemtype elements can be considered.
Here is an example of standard HTML that might be entered by code or produced by PHP or ASP:
<h1>A Night at the Opera
<span>Artist: Queen (formed 1971)</span>
<span>Rock, heavy metal</span>
<a href="../albums/queen-night-opera.html">Buy the album</a>
This entry for the rock band Queen’s fourth album might be enhanced with microdata thus:
<div itemscope itemtype ="http://schema.org/music">
<h1 itemprop="name">A Night at the Opera</h1>
<span>Artist: <span itemprop="artist">Queen</span> (formed 1971)</span>
<span itemprop="genre"> Rock, heavy metal </span>
<a href="../albums/queen-night-opera.html " itemprop="album"> Buy the album </a>
As you can see, the length of the HTML is almost doubled. Another impact of microdata could be an increase in page load times on slower connections.