Still confused about using MVVM with the TabbedMdiHost

Hello,

I have looked through the samples and read through the forums, and I am still confused about how to create tabs automatically to match an ObservableCollection in my ViewModel.  It seems like doing this should be a lot simpler than what I am seeing, so I am hoping that there is something fundamental that I don't understand and that you can quickly clear up.

Here is my code:

<Window x:Class="ActiproTest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:local="clr-namespace:ActiproTest"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:docking="http://schemas.actiprosoftware.com/winfx/xaml/docking" 
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <local:MainViewModel x:Key="MainViewModelDataSource" />
        <DataTemplate x:Key="DocItemTemplate">
            <TextBlock Text="Yippee!" />
        </DataTemplate>
        <Style x:Key="DockingItemStyle" TargetType="docking:DockingWindow">
            <Setter Property="Description" Value="{Binding Text}" />
            <Setter Property="Title" Value="{Binding Title}" />
        </Style>
        <!-- docking:DocumentWindow -->
        <Style x:Key="DocumentItemStyle" TargetType="docking:DocumentWindow" BasedOn="{StaticResource DockingItemStyle}">
            <Setter Property="FileName" Value="{Binding Title}" />
            <Setter Property="IsReadOnly" Value="True" />
        </Style>
    </Window.Resources>
    <Grid DataContext="{Binding Source={StaticResource MainViewModelDataSource}}">
        <docking:DockSite  DocumentItemsSource="{Binding DocumentViewModels}" DocumentItemTemplate="{StaticResource DocItemTemplate}" DocumentItemContainerStyle="{StaticResource DocumentItemStyle}">
            <docking:DockSite.AutoHideLeftContainers>
                <docking:ToolWindowContainer >
                    <docking:ToolWindow Title="Analyzers">
                        <TextBlock Text="The palette..." />
                    </docking:ToolWindow>
                </docking:ToolWindowContainer>
            </docking:DockSite.AutoHideLeftContainers>
            <docking:DockSite.AutoHideRightContainers>
                <docking:ToolWindowContainer>
                    <docking:ToolWindow Title="Settings">
                        <TextBlock Text="Some settings..." />
                    </docking:ToolWindow>
                </docking:ToolWindowContainer>
            </docking:DockSite.AutoHideRightContainers>
            <docking:DockSite.AutoHideBottomContainers>
                <docking:ToolWindowContainer>
                    <docking:ToolWindow Title="Log" />
                    <docking:ToolWindow Title="Errors" />
                </docking:ToolWindowContainer>
            </docking:DockSite.AutoHideBottomContainers>
            <docking:Workspace>
                <docking:TabbedMdiHost />
            </docking:Workspace>
        </docking:DockSite>
    </Grid>
</Window>

using System.Collections.ObjectModel;

namespace ActiproTest
{
    public class MainViewModel
    {
        private ObservableCollection<DocumentViewModel> _documentViewModels = new ObservableCollection<DocumentViewModel>(); 

        public ObservableCollection<DocumentViewModel> DocumentViewModels
        {
            get { return _documentViewModels; }
        }

        public MainViewModel()
        {
            _documentViewModels.Add(new DocumentViewModel("Document 1", "Hello, how are you?"));
            _documentViewModels.Add(new DocumentViewModel("Doc 2", "Great! Thanks :)"));
        }
    }
}

namespace ActiproTest
{
    public class DocumentViewModel
    {
        public string Title { get; private set; }
        public string Text { get; private set; }

        public DocumentViewModel(string title, string text)
        {
            Title = title;
            Text = text;
        }
    }
}

Thanks a lot,

-Erin