Dijkgraaf - 3:09 am on Jan 27, 2012 (gmt 0)

Yes, if the schema specifies the the elements should be in a particular sequence (some schemas don't) then they need to be in that exact sequence.

Yes, XML is case sensitive and your XML nodes/elements need to match the case exactly.

This schema expect things in sequence
<?xml version="1.0" encoding="utf-16"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="RateV4Request">
<xs:complexType>
<xs:sequence>
<xs:element name="Revision" type="xs:unsignedByte" />
<xs:element name="Package">
<xs:complexType>
<xs:sequence>
<xs:element name="Service" type="xs:string" />
<xs:element name="ZipOrigination" type="xs:unsignedInt" />
<xs:element name="ZipDestination" type="xs:unsignedInt" />
<xs:element name="Pounds" type="xs:unsignedByte" />
<xs:element name="Ounces" type="xs:unsignedByte" />
<xs:element name="Container" type="xs:string" />
<xs:element name="Size" type="xs:string" />
<xs:element name="Width" type="xs:unsignedByte" />
<xs:element name="Length" type="xs:unsignedByte" />
<xs:element name="Height" type="xs:unsignedByte" />
<xs:element name="Machinable" type="xs:string" />
</xs:sequence>
<xs:attribute name="ID" type="xs:string" use="required" />
</xs:complexType>
</xs:element>
</xs:sequence>
<xs:attribute name="USERID" type="xs:string" use="required" />
</xs:complexType>
</xs:element>
</xs:schema>

This one doesn't
<?xml version="1.0" encoding="utf-16"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="RateV4Request">
<xs:complexType>
<xs:all minOccurs="1" maxOccurs="1">
<xs:element name="Revision" type="xs:unsignedByte" />
<xs:element name="Package">
<xs:complexType>
<xs:all minOccurs="1" maxOccurs="1">
<xs:element name="Service" type="xs:string" />
<xs:element name="ZipOrigination" type="xs:unsignedInt" />
<xs:element name="ZipDestination" type="xs:unsignedInt" />
<xs:element name="Pounds" type="xs:unsignedByte" />
<xs:element name="Ounces" type="xs:unsignedByte" />
<xs:element name="Container" type="xs:string" />
<xs:element name="Size" type="xs:string" />
<xs:element name="Width" type="xs:unsignedByte" />
<xs:element name="Length" type="xs:unsignedByte" />
<xs:element name="Height" type="xs:unsignedByte" />
<xs:element name="Machinable" type="xs:string" />
</xs:all>
<xs:attribute name="ID" type="xs:string" use="required" />
</xs:complexType>
</xs:element>
</xs:all>
<xs:attribute name="USERID" type="xs:string" use="required" />
</xs:complexType>
</xs:element>
</xs:schema>