I found that xmllint provides the functionality I was looking for. I'd like to step through what I've been doing to test my XML/XSD validation.
1. Create the XSD file. I'll use an example from W3Schools. Save the following to a file named note.xsd:
<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.w3schools.com"
xmlns="http://www.w3schools.com"
elementFormDefault="qualified">
<xs:element name="note">
<xs:complexType>
<xs:sequence>
<xs:element name="to" type="xs:string"/>
<xs:element name="from" type="xs:string"/>
<xs:element name="heading" type="xs:string"/>
<xs:element name="body" type="xs:string"/>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>
2. Create the XML file. Again, we'll use an example from W3Schools. Save the following to a file named note.xml:
<?xml version="1.0"?>
<note xmlns="http://www.w3schools.com"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3schools.com note.xsd">
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>
3. Validate the XML against the Schema. You will need to have xmllint installed. I type the following on the command line for validation:
xmllint --noout --schema note.xsd note.xml
This gives me the following output:
note.xml validates
Now that we know what happens for passing validation, I'd like to show you a failing one. Let's change the order of the elements in our XML. This will cause the validation to fail because the order is explicit per our XSD. The following XML switches the to and from elements:
<?xml version="1.0"?>
<note xmlns="http://www.w3schools.com"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3schools.com note.xsd">
<from>Jani</from>
<to>Tove</to>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>
This will give the following output when we run xmllint:
note.xml:5: element from: Schemas validity error : Element '{http://www.w3schools.com}from': This element is not expected. Expected is ( {http://www.w3schools.com}to ).
note.xml fails to validate
I'm a little disappointed with the error message that I receive, but I think I'll gain a better understanding of them as I use the tool more.
