11.1 The Syntax of Microdata 265At first glance, the many curly and square brackets may seem confusing, but
they disclose the metadata structure very clearly if you look closer. Each entry
(“items”) consists of an array of properties (“properties”), which are in turn made
up of name-value pairs with the name of the property (“musician”) and the corre-
sponding values (“Pat Metheny,” “Antonio Sanchez,” “Steve Rodby,” “Lyle Mays”)
as an array.
Some HTML elements automatically define the value of the specified property
as soon as an itemprop attribute is assigned to them. Let’s use the blog entry’s
descriptive picture to test the microdata viewer and give it an itemprop attri-
bute image:
This automatically gives us the value of the src attribute as the value for the prop-
erty image. In addition to the img element, there are a number of other elements
to which this behavior applies. You can see them in Table 11.1.
Table 11.1 Elements with special “itemprop” values
Attribute Element(s)src audio, embed, iframe, img, source, video
href a, area, linkdatetime time
content metadata objectLet’s turn back to the spider, which is now indexing our microdata-filled blog.
It won’t know what to make of the items musician and image. The reason is be-
cause we have defined our own microdata terms that have meaning only to us.
To be able to use microdata sensibly, we need standardized dialects that can be
comprehended by our spider, just as by an intelligent mail program that auto-
matically extracts e-mail addresses encoded as microdata if you drag a URL into
its address book, or by a diary able to recognize diary dates by the same method.