Simple Element Types with Extended Data Types

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∟Simple Element Types with Extended Data Types

This section describes simple element types using data types extended from XML Schema built-in data types. Data types can be extended with restrictions, union or list operations.

Simple XML Element Type: An XML element that has no child elements and no attributes. Simple XML elements can be defined by using XSD built-in data types. They can also be defined by using extended data types, which are defined by "simpleType" statements:

<xsd:simpleType name="my_type_name">
 <xsd:restriction base="xsd:type_name">
  XSD facet statements
 </xsd:restriction>
</xsd:simpleType>
<xsd:element name="element_name" type="my_type_name"/>

where "element_name" is the name of the XML element, "xsd:type_name" is a pre-defined data type serving as the base data type, and "my_type_name" is the new data type extended from the base data type.

Optional facet statements can be enclosed in the "restriction" statement to provide additional restrictions to the extended data type:

xsd:minInclusive - Inclusive minimum value.
xsd:minExclusive - Exclusive minimum value.
xsd:maxInclusive - Inclusive maximum value.
xsd:maxExclusive - Exclusive maximum value.
xsd:enumeration - One valid value. Repeat this statement to provide multiple values.
xsd:whiteSpace - How to handle white spaces: "preserve|replace|collapse".
xsd:pattern - A regular expression the value must match.
xsd:length - Number of characters.
xsd:minLength - Minimum number of characters.
xsd:maxLength - Maximum number of characters.
xsd:totalDigits - Maximum number of digits.
xsd:fractionDigits - Maximum number of digits in the fraction part.

The syntax of facet statement is:

<xsd:facet_name value="facet_value">

Besides restricting the base data types to extend new data types, we can also extend new data types by define "union" or "list" of base data types.

Union: A collection of base data types. A value is valid for a union data type if and only it is valid for one of the base data types.

<xsd:simpleType name="my_type_name">
 <union>
  <xsd:restriction base="xsd:type_name_1">
   XSD facet statements
  </xsd:restriction>
  <xsd:restriction base="xsd:type_name_2">
   XSD facet statements
  </xsd:restriction>
 </union>
</xsd:simpleType>
<xsd:element name="element_name" type="my_type_name"/>

List: A data type for lists of values of a base data type. The list of values must be white space delimited. For example, the following code

<xsd:simpleType name="integerList">
 <list>
  <xsd:restriction base="xsd:integer">
   <xsd:minInclusive value="1">
   <xsd:maxInclusive value="49">
  </xsd:restriction>
 </list>
</xsd:simpleType>
<xsd:element name="winning_numbers" type="integerList"/>