EPMDocument - Root Document

I have the follwoing scenario:

I have a package which during the workflow i extract the various EPMDocuments and download to disk.

The document is a burst document which requires to be re-constructed. that part is all done and complete.

Now, I need to identify which is the root or top most document so I can delete the burst documents from disk.

Using the API, how can I identify if the EPMDocument is the top most document?

When I look at the document in Arbortext Content manager, I see that the top most document does not contain any usage attributes.

Is this a safe way to identify the root document and if so, how would I get the usage attributes for a document using the API.

Any suggestions or advice is most welcome.

Thanks