Vista - Schema Design Question

Ok, I'm stumped here.

Suppose I have a schema consisting of publishers and books. Each book is
published by one and only one publisher. So in the classic sense it's a
"one to many" relationship.

My schema looks something like this:

<EntityType Name="Publisher" BaseType="Contacts.Organization">
<Documentation>...</Documentation>
<ChangeUnit Name="Publisher" Id="1" />
</EntityType>

<EntityType Name="Title" BaseType="Storage.Item">
<Documentation>...</Documentation>
<ChangeUnit Name="Title" Id="1" />
<Property Name="Volume" Type="Storage.Int32" Nullable="true"
ChangeUnit="Title" />
<Property Name="Year" Type="Storage.Int16" Nullable="true"
ChangeUnit="Title" />
<Property Name="Details" Type="Storage.String" Size="2000"
Nullable="true" ChangeUnit="Title" />
</EntityType>

How do I associate these two items?

I have tried adding an Association, like this:

<Association Name="PublisherTitles">
<Documentation>...</Documentation>
<End Role="Publisher" PluralRole="Publishers"
Type="Comicster.Publisher" />
<End Role="Title" PluralRole="Titles" Type="Comicster.Title" />
<Reference FromRole="Publisher" Property="Titles" ToRole="Title" />
</Association>

.... but that throws "error AG0066: Invalid Property on AssociationEntity
Reference. Property Titles is not a member of type
MadProps.Comicster.Storage.Publisher."

How do I define the "Publisher.Titles" property that gives me a list of
that publisher's titles? Or conversely, how can I define a
"Title.Publisher" property that refers back to the title's publisher?

I'm just finding it difficult to make the mental leap from classical
database design to WinFS schema design.

Thanks in advance,
Matt