XSD Simple Elements
XML模式s define the elements of your XML files.
A simple element is an XML element that contains only text. It cannot contain any other elements or attributes.
What is a Simple Element?
A simple element is an XML element that can contain only text. It cannot contain any other elements or attributes.
However, the "only text" restriction is quite misleading. The text can be of many different types. It can be one of the types included in the XML模式 definition (boolean, string, date, etc.), or it can be a custom type that you can define yourself.
You can also add restrictions (facets) to a data type in order to limit its content, or you can require the data to match a specific pattern.
Defining a Simple Element
The syntax for defining a simple element is:
where xxx is the name of the element and yyy is the data type of the element.
XML模式 has a lot of built-in data types. The most common types are:
Here are some XML elements:
And here are the corresponding simple element definitions:
<xs:element name="age" type="xs:integer"/>
<xs:element name="dateborn" type="xs:date"/>
Default and Fixed Values for Simple Elements
Simple elements may have a default value OR a fixed value specified.
A default value is automatically assigned to the element when no other value is specified.
In the following example the default value is "red":
A fixed value is also automatically assigned to the element, and you cannot specify another value.
In the following example the fixed value is "red":