XML schema privides a mechanism to bound the values of elements and attributes to concrete data types, like integer and date. This information will be used by validator-tool to check the document for validity as well as parse value to final laguage-based types. XML schema contsaines a huge set of predefined simple data types. In our sample schema we'll use them to define some attributes:

 <xs:element name="purchase-order">

////////////// define date attribute of type date:
    <xs:attribute name="date" type="xs:date" use="required"/>

////////////// order number should be an integer:
    <xs:attribute name="number" type="xs:integer" use="required"/>

////////////// both attributes are marked as 'required', thus absence of each 
////////////// one of them will lead a validation error;
  ...
////////////// element can also have a primitive value:
              <xs:element name="address" type="xs:string"/>
  ...
  </xs:element>
</xs:schema>