[flexcoders] reference to Data Provider throws error

[tex_learning_flex]

I have in my base mxml file:

[Bindable]
public var myDP:ArrayCollection;

which is a DataProvider

elsewhere I have an mxml component file with a Spark List. I the list I have 
specified:

<s:List
        id="list"
        dataProvider="{myDP}"
        itemRenderer="assets.Renderer"
        >

this file is throwing the following error:

1120: Access of undefined property myDP.

any idea what might be wrong?