XSD Tutorials - Herong's Tutorial Examples - Version 5.10, by Dr. Herong Yang
Deriving New Simple Datatypes - "simpleType" Element
This section describes a tutorial example on how to define a simple datatype based on a built-in datatype by adding restriction facets.
Sometime, you want to modify a built-in datatype by adding some restrictions. This can be done by using the Simple Type Definition Component.
For example, I want design a schema to validate an XML element called "age". I could use the built-in datatype "nonNegativeInteger". But I want restrict the value to be less or equal to 150. I can use the Simple Type Definition Component to modify "nonNegativeInteger" in this case.
Rule 1. The Simple Type Definition Component allows you to define a new simple datatype based on an existing simple datatype, including any built-in datatype.
Rule 2. The XML representation of a Simple Type Definition Component is an "simpleType" element, which must have one sub element of "restriction", "list", or "union". The sub element provides base datatypes and modification details.
Rule 3. A "simpleType" element must have "name" attribute, if it is used to define a named datatype.
Here is the schema document, age.xsd. It defines a derived simple datatype "ageType", which is derived from the built-in datatype "nonNegativeInteger" with a restriction of a maximum value.
<?xml version="1.0"?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <!-- age.xsd - Copyright (c) 2013, HerongYang.com, All Rights Reserved. --> <!-- Using a derived simple datatype --> <xs:element name="age" type="ageType"/> <!-- Defining "ageType" based on "string" --> <xs:simpleType name="ageType"> <xs:restriction base="xs:nonNegativeInteger"> <xs:maxInclusive value="150"/> </xs:restriction> </xs:simpleType> </xs:schema>
Obviously, the following XML document, age_error.xml, does not conform the schema document, age.xsd:
<?xml version="1.0"?> <age>200</age>
Here is the output of XsdSchemaValidator.java:
>java XsdSchemaValidator age.xsd age_error.xml Error: Line number: 2 Column number: 15 Message: cvc-maxInclusive-valid: Value '200' is not facet-valid with respect to maxInclusive '150' for type 'ageType'. Error: Line number: 2 Column number: 15 Message: cvc-type.3.1.3: The value '200' of element 'age' is not valid. Failed with errors: 2
Note that the "maxInclusive" sub element is called a restriction "facet". Different built-in datatypes support different sets of facets. For more information, read the built-in datatype chapter in this book.
Last update: 2013.
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