Why won't XML Schema allow me to define a one-to-many key? And how do I do so? - xsd

Question

I'm falling over on a frustrating, arbitrary restriction in XML Schema. For some reason, it insists that PK-FK relationships have to be one-to-one. Why?
For example, given the schema:
<?xml version="1.0" encoding="utf-8"?>
<xs:schema id="FutureSchema"
targetNamespace="http://tempuri.org/FutureSchema.xsd"
elementFormDefault="unqualified"
xmlns="http://tempuri.org/FutureSchena.xsd"
xmlns:mstns="http://tempuri.org/FutureSchema.xsd"
xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="FUTUREFILE">
<xs:complexType>
<xs:sequence>
<xs:element name="Configuration">
<xs:complexType>
<xs:sequence>
<xs:element name="Experiments">
<xs:complexType>
<xs:sequence>
<xs:element name="Experiment">
<xs:complexType>
<xs:attribute name="ID" type="xs:integer"/>
<xs:attribute name="Profile" type="xs:integer"/>
</xs:complexType>
<xs:keyref name="dummy" refer="LP">
<xs:selector xpath="Experiment"/>
<xs:field xpath="#Profile"/>
</xs:keyref>
</xs:element>
</xs:sequence>
</xs:complexType>
<xs:key name="LP">
<xs:selector xpath="*/Configuration/Profiles/Profile"/>
<xs:field xpath="#ID"/>
</xs:key>
</xs:element>
<xs:element name="Profiles">
<xs:complexType>
<xs:sequence>
<xs:element name="Profile">
<xs:complexType>
<xs:attribute name="ID" type="xs:integer"/>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>
And an example instance:
<?xml version="1.0" encoding="utf-8" ?>
<b:FUTUREFILE xmlns:b="http://tempuri.org/FutureSchena.xsd">
<Configuration>
<Experiments>
<Experiment ID="1" Profile="1"/>
<Experiment ID="2" Profile="1"/>
</Experiments>
<Profiles>
<Profile ID="1"/>
</Profiles>
</Configuration>
</b:FUTUREFILE>
Document validation throws an error if I define <Experiment ID="1" FK="1"/><Experiment ID="2" FK="1"/>, for example; i.e. more than one Experiment may not reference the same Profile. But why else would I want to use a key relationship? What use is a key relationship at all if I can't do something so fundamental?
OK, if and won't let me do this, how should I?
edit #1: As requested, I've padded out my code sample to include the full schema and a basic instance.
edit #2: Interesting. SharpDevelop's XML editor (as opposed to Visual Studio's) doesn't seem to object. It doesn't object to the foreign key value referring to a nonexistent primary key either (which IMO it should) but it's a start.

Answer 1

What wasn't clear ?... My english, it's all :-)
Some remarqs, I'm not sure it's solution :
In exemple instance, it's best to use xmlns:b="http://tempuri.org/FutureSchema.xsd">, and not xmlns:b="http://tempuri.org/FutureSchena.xsd"> (n -> m).
Also it's best to put b: in front of all elements names.
According to your schema, you can't have two Experiment in Experiments, only one.
On xsd, put <xs:keyref name="dummy" refer="mstns:LP">, that works best for me ; it's because xpath expression doesnt't understand default namespace, see Correct way to use key in xsd.