Xerces reports error when giving attribute to top-level element - xsd

Question

I have the following schema which works fine:
<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="bindings">
<xs:complexType>
<xs:sequence maxOccurs="unbounded">
<xs:element name="bind">
<xs:complexType>
<xs:attribute name="trigger" use="required">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:minLength value="1"/>
</xs:restriction>
</xs:simpleType>
</xs:attribute> <!-- trigger -->
<xs:attribute name="command" use="required">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:minLength value="1"/>
</xs:restriction>
</xs:simpleType>
</xs:attribute> <!-- command -->
</xs:complexType>
</xs:element> <!-- bind -->
</xs:sequence>
</xs:complexType>
</xs:element> <!-- bindings -->
</xs:schema>
However, when I try to define an attribute for the top level bindings element, I get an error no matter where I place the attribute code. What am I missing or doing wrong?
EDIT: It looks like there's some problem with either my Java XML code or Xerces. If I change the XSD to give the top-level element the optional "parent" attribute, Xerves gives me the error "Problem: schema_reference.4: Failed to read schema document 'null', because 1) could not find the document; 2) the document could not be read; 3) the root element of the document is not <xsd:schema>." However, if I give the attribute any name //other// than "parent", it reports Attribute 'parent' is not allowed to appear in element 'bindings'., just as you'd expect.
My Java code regarding XSD and Xerces is:
bindingsDocumentBuilderFactory =
DocumentBuilderFactory.newInstance();
DocumentBuilderFactory bdbf = bindingsDocumentBuilderFactory;
bdbf.setValidating(true);
// I get the input stream here as "is"
bdbf.setAttribute("http://java.sun.com/xml/jaxp/properties/schemaLanguage",
"http://www.w3.org/2001/XMLSchema");
bdbf.setAttribute("http://java.sun.com/xml/jaxp/properties/schemaSource", is);
EDIT 2:
The XML file which is being validated:
<bindings parent="game/movement">
<bind trigger="i" command="INVENTORY"/>
</bindings>

Answer 1

This works (see attribute named code):
<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="bindings">
<xs:complexType>
<xs:sequence maxOccurs="unbounded">
<xs:element name="bind">
<xs:complexType>
<xs:attribute name="trigger" use="required">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:minLength value="1"/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
<!-- trigger -->
<xs:attribute name="command" use="required">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:minLength value="1"/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
<!-- command -->
</xs:complexType>
</xs:element>
<!-- bind -->
</xs:sequence>
<xs:attribute name="code"/>
</xs:complexType>
</xs:element>
<!-- bindings -->
</xs:schema>