XML Tutorial/XML Schema/positiveInteger

The positiveInteger datatype is derived from the nonNegativeInteger type.

The value space is the infinite set of integers greater than or equal to 1. 
The lexical space is a finite-length sequence of decimal digits with an optional leading +.
<!-- schema -->
<xsd:complexType name="record_sets">
  <xsd:sequence>
   <xsd:element name="record" minOccurs="0"
    maxOccurs="unbounded">
    <xsd:simpleType>
     <xsd:restriction base="xsd:positiveInteger">
      <xsd:pattern value="555\d{3}"/>
     </xsd:restriction>
    </xsd:simpleType>
   </xsd:element>
  </xsd:sequence>
</xsd:complexType>
<!-- instance document -->
<record>555158</record>
<record>555687</record>
<record>555736</record>

Use positiveInteger

File: Schema.xml
<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
  targetNamespace="http://www.wbex.ru" 
  xmlns="http://www.wbex.ru"
  elementFormDefault="qualified">
  <xs:element name="population" type="xs:positiveInteger" />
</xs:schema>

File: Data.xml
<?xml version="1.0"?>
<population xmlns="http://www.wbex.ru">342</population>