XSD Attributes

All attributes are declared as simple types.

What is an Attribute?

Simple elements cannot have attributes. If an element has attributes, it is considered to be of a complex type. But the attribute itself is always declared as a simple type.

How to Define an Attribute?

The syntax for defining an attribute is:

<xs:attribute name="xxx" type="yyy"/>

XML Schema has a lot of built-in data types. The most common types are:

• xs:string
• xs:decimal
• xs:integer
• xs:boolean
• xs:date
• xs:time

Example

Here is an XML element with an attribute:

<lastname lang="EN">Smith</lastname>

And here is the corresponding attribute definition:

<xs:attribute name="lang" type="xs:string"/>

Default and Fixed Values for Attributes

Attributes may have a default value OR a fixed value specified.

A default value is automatically assigned to the attribute when no other value is specified.

In the following example the default value is "EN":

<xs:attribute name="lang" type="xs:string" default="EN"/>

A fixed value is also automatically assigned to the attribute, and you cannot specify another value.

In the following example the fixed value is "EN":

<xs:attribute name="lang" type="xs:string" fixed="EN"/>

Optional and Required Attributes

Attributes are optional by default. To specify that the attribute is required, use the "use" attribute:

<xs:attribute name="lang" type="xs:string" use="required"/>

Restrictions on Content

When an XML element or attribute has a data type defined, it puts restrictions on the element's or attribute's content.

If an XML element is of type "xs:date" and contains a string like "Hello World", the element will not validate.

With XML Schemas, you can also add your own restrictions to your XML elements and attributes. These restrictions are called facets. You can read more about facets in the next chapter.

Get Your Diploma! W3Schools' Online Certification Program is the perfect solution for busy professionals who need to balance work, family, and career building. The HTML Certificate is for developers who want to document their knowledge of HTML, XHTML, and CSS. The ASP Certificate is for developers who want to document their knowledge of ASP, SQL, and ADO.

Jump to: Top of Page or HOME or Printer friendly page

W3Schools provides material for training only. We do not warrant the correctness of its contents. The risk from using it lies entirely with the user. While using this site, you agree to have read and accepted our terms of use and privacy policy.

Copyright 1999-2008 by Refsnes Data. All Rights Reserved.

W3Schools was converted to XHTML in December 1999