XSD Restrictions/Facets

When an XML element or attribute 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 contains a string like "Hello World", the element will not validate.
With XML Schemas, you can also add your own restrictions to your XML elements and attributes. These restrictions are called facets.

In otherwards,Restrictions are used to define acceptable values for XML elements or attributes. Restrictions on XML elements are called facets.

The following type of restrictions are allowed in xml schema:
Restrictions on Values
Restrictions on a Series of Values
Restrictions on Whitespace Characters
Restrictions on Length
Restrictions for Datatypes and
Other Restrictions on a Series of Values