Product Version: NetBeans IDE Dev (Build 201112270601)
Java: 1.7.0_01; Java HotSpot(TM) 64-Bit Server VM 21.1-b02
System: Windows 7 version 6.1 running on amd64; Cp1252; en_US (nb)
User directory: C:\Users\deuggercz\.netbeans\dev
Cache directory: C:\Users\deuggercz\.netbeans\dev\var\cache

Steps:
1. Use File | New Project... to create new Web Application project located in
your home directory.
2. Invoke File | New File... from main menu.
3. Select XML category and XML Schema (empty) as file type. Push Next.
4. Type addressbook into File Name, change Folder field to src\java\schema (on
Windows platform is \ and on Un*x is / as separator) and press Finish.
5. Copy this content:

<?xml version="1.0" encoding="ISO-8859-1" ?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">

<xsd:simpleType name="EmailType">
    <xsd:restriction base="xsd:string">
        <xsd:pattern value="[a-z.]*@[a-z]*.[a-z]*"/>
    </xsd:restriction>
</xsd:simpleType>

<xsd:complexType name="FriendType">
    <xsd:sequence>
        <xsd:element name="email" type="EmailType" minOccurs="1"/>
    </xsd:sequence>
    <xsd:attribute name="nickname" use="required" type="xsd:string"/>
    <xsd:attribute name="birthday" type="xsd:date"/>
</xsd:complexType>

<xsd:element name="addressbook">
    <xsd:complexType>
        <xsd:sequence>
            <xsd:element name="friend" type="FriendType" maxOccurs="unbounded"/>
        </xsd:sequence>
    </xsd:complexType>
</xsd:element>
</xsd:schema>

into clipboard.
6. Invoke File | New File... from main menu.
7. Select XML category and XML Document as file type. Push Next.
8. Type addressbook into File Name, change Folder to src\java\schema (on Windows platform is \ and on Un*x is / as separator) and press Next.
9. Select XML Schema-Constrained Document option and push Next.
10. Push Browse and pick up addressbook.xsd. Also check Import during selecting addressbook.xsd
11. If everything is alright check Primary
12. Push Next and than Finish.
13. Right click editor area and choose Validate XML from popup menu.

There are several errors reported in Output - XML check window. 

For instance:
TargetNamespace.1: Expecting namespace 'null', but the target namespace of the schema document is 'null'. [2] 
cvc-elt.1: Cannot find the declaration of element 'ns1:addressbook'. [11]