To specify the number of digits in a number : precision « XML Schema « XML Tutorial

1. XML Tutorial
2. XML Schema
3. precision

You can limit the number of digits to the right or left of the decimal point of a number.
xsd:precision facet must be a positive number (1, 2, 3, or higher). 
xsd:precision may not be equal to zero. 
xsd:precision may not be less than the xsd:scale value.
xsd:scale facet must be a non-negative integer (0, 1, 2, or higher).
Both the xsd:precision and xsd:scale facets specify the maximum values allowed. 
The number is still considered valid if fewer digits are present.
You may set a xsd:precision and xsd:scale for any numerical type, but not for any string, date, or other types.


File: Schema.xsd
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
  targetNamespace="http://www.java2s.com" xmlns="http://www.java2s.com"
  elementFormDefault="qualified">

  <xsd:element name="numbers">
    <xsd:simpleType>
      <xsd:restriction base="xsd:decimal">
        <xsd:precision value="5" />
        <xsd:scale value="2" />
      </xsd:restriction>
    </xsd:simpleType>
  </xsd:element>
</xsd:schema>


File: Data.xml
<?xml version="1.0"?>
<numbers xmlns="http://www.java2s.com">34.5</numbers>