XML schema validation and ignorable whitespace

XML schema validation removes ignorable whitespace from a document.

According to the XML standard, whitespace is space characters (U+0020), carriage returns (U+000D), line feeds (U+000A), or tabs (U+0009) that are in the document to improve readability. When any of these characters appear as part of a text string, they are not considered to be whitespace.

Ignorable whitespace is whitespace that can be eliminated from the XML document. The XML schema document determines which whitespace is ignorable whitespace. If an XML document defines an element-only complex type (an element that contains only other elements), the whitespace between the elements is ignorable. If the XML schema defines a simple element that contains a non-string type, the whitespace within that element is ignorable.

Example: The description element in the sample product.xsd XML schema document is defined like this:

<xs:element name="description" minOccurs="0" maxOccurs="unbounded">
  <xs:complexType>
    <xs:sequence>
      <xs:element name="name" type="xs:string" minOccurs="0" />
      <xs:element name="details" type="xs:string" minOccurs="0" />
      <xs:element name="price" type="xs:decimal" minOccurs="0" />
      <xs:element name="weight" type="xs:string" minOccurs="0" />
 …
 </xs:complexType>
</xs:element>

The description element has an element-only complex type because it contains only other elements. Therefore, whitespace between elements in a description element is ignorable whitespace. The price element can also contain ignorable whitespace because it is a simple element that contains a non-string type.

Suppose that schema PRODUCT is registered in the XML schema repository (XSR).

Suppose that you create table MYPRODUCT like this:

CREATE TABLE MYPRODUCT (
 PID VARCHAR(10) NOT NULL PRIMARY KEY,
 NAME VARCHAR(128),
 PRICE DECIMAL(30,2),
 PROMOPRICE DECIMAL(30,2),
 PROMOSTART DATE,
 PROMOEND DATE,
 DESCRIPTION XML)

You insert the following document into XML column DESCRIPTION in the MYPRODUCT table, and you validate the XML data against the XML schema document product.xsd, which is located in the XML schema repository on the same database server as the MYPRODUCT table.

<product xmlns="http://posample.org" pid="110-100-01" >
 <description>
 <name>Anvil</name>
 <details>Very heavy</details>
 <price>         9.99            </price>
 <weight>1 kg</weight>
 </description>
</product>

When you retrieve the stored data, you can see that the XML schema validation process removes ignorable whitespace. The retrieved data is a single line with the following content:

<product xmlns="http://posample.org" pid="110-100-01"><description><name>Anvil
</name><details>Very heavy</details><price>9.99</price><weight>1 kg</weight>
</description></product>

The PRODUCT schema defines the whitespace around the name, details, price, and weight elements, and the whitespace within the price element as ignorable whitespace, so XML schema validation removes it.