Question

Could someone please explain to me a bit about this XML schema. I have been reading for hours but I can’t figure out the part of the restriction part, and what are those restricted values suppose to mean?

<?xml version="1.0" encoding="utf-8"?>
<xs:schema elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="storagehouse">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="item" maxOccurs="unbounded">

        <xs:complexType>
          <xs:sequence>
            <xs:element name="name" type="xs:string"  minOccurs="0"/>
            <xs:element name="weight" type="xs:float"  minOccurs="0"/>
            <xs:element name="category" type="xs:string" />
            <xs:element name="location" minOccurs="0">
              <xs:simpleType>
                <xs:restriction base="xs:string">
                  <xs:enumeration value="A1" />
                  <xs:enumeration value="A2" />
                  <xs:enumeration value="A3" />
                  <xs:enumeration value="A4" />
                  <xs:enumeration value="B1" />
                  <xs:enumeration value="B2" />
                  <xs:enumeration value="B3" />
                  <xs:enumeration value="B4" />
                  <xs:enumeration value="C1" />
                  <xs:enumeration value="C2" />
                  <xs:enumeration value="C3" />
                  <xs:enumeration value="C4" />
                  <xs:enumeration value="D1" />
                  <xs:enumeration value="D2" />
                  <xs:enumeration value="D3" />
                  <xs:enumeration value="D4" />
                </xs:restriction>
              </xs:simpleType>
            </xs:element>
      </xs:sequence>
      <xs:attribute name="id" type="xs:string" use="required"/>
      </xs:complexType>
        </xs:element>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>

Answer 1

Explanation of the restriction part:

• The element called location is an element of simple type with restriction.

• The restriction element defines restrictions on a set of values : The only acceptable values for the element locationare “A1”, “A2”, … , “D3”, “D4”.