public interface DirectLoadingDocumentFormat
DocumentFormat which will read directly from an URL by itself.
If a DocumentFormat subclass implements this
interface, the code normally responsible for reading the document content
when the Document instance is created will will skip reading from the URL
and delegate the reading to the implementing document format.
If a document is created from a String (i.e. sourceUrl is null),
the document format will decide what to do and this interface is
not relevant.