All attributes are declared as the simple types.

Simple elements cannot have attribute. If an element has attributes, it is considered to be of a complex types. But the attribute itself is declared as a simple type.

The syntax for defining an attribute is as follows:

where xxx is the name of the attribute and yyy specify the data type of the attribute.

XML Schema has a lot of built-in data type. The most common types are as follows:

• xs:string
• xs:decimal
• xs:boolean
• xs:integer
• xs:date
• xs:time

Here is an XML element with attribute:

Attributes may havedefault value OR a fixed value specified.

A default value is automatically assigned to the attributes when no other value is specified.

In the following example the default value for the attribute is "EN":

A fixed value is also automatically assigned to the attribute, and you cannot specify another value.

In the following example the fixed value is "EN":

Attributes are by default optional. To specify that the attributes are required, use the "use" attribute:

When an XML elements or attributes has a data type defined, it puts restrictions on the element's or attribute's content.

If an XML element is of type "xs:date" and contain a string like "Hello World", the element will not validate.

With XML Schema, you can also add your own restrictions to your XML elements and attributes. These restrictions are called facet. You can also read more about facets in the next chapter.