Hello
I believe that the way the different data are linked together only depends on how we want to manage and control them.
An attachment cannot be iterated, version controlled, searchable, reuse etc.. It is a very static piece of information which only relevant to the Document (EPM or WT) it is attached to. When the document is released the attached content must be correct that all.
It is also difficult for other users to know if there is an attachment. There is no provision in the folder view for instance unlike discussion.
An example would be a jpg used by the designer to create his model.
However, if the file which is supposed to be attached , is actually a reference document, ie it is related but it must/can be controlled, managed (life cycle state), revised, have soft attributes etc.. then a document must be created and the file will be uploaded in that document. That document will then be used in a WTpart, if it is part of the WTPart definition. Between WTdocument, it is possible to create a document structure or to create references between the WTdocument.
They are different ways to "linked" information. It all depends on what we want to do with it. The bottom line is that whatever is decided in your organisation, all users should follow the same process. Other you will never be able to find the data or understand them (a reference document does not mean the same thing than an attached document for instance)
