CCXML <startdialog> question

Dear group,

I would highly appreciate if someone would clarify usage of connectionid and conferenceid 
attributes of <startdialog> element.

The question is:
Is it possible to start a dialog which is not joined with a connection or a conference, and join the dialog later by an explicit <join>?

The specification states the following:

"If both the connectionid and the conferenceid are omitted and the dialog was previously prepared using a dialogprepare element with a connectionid or conferenceid specified, the interpreter must use the id as specified on the dialogprepare element.
If neither the connectionid or conferenceid is specified and the dialog had not previously been prepared, the interpreter must use the id indicated in the current event being processed."

But specification doesn't say what happens if the current event is not a connection or conference event, and so doesn't have a connection or conference id. Is it an error, or is it allowed, meaning that the dialog is not joined with a connection or conference?

Thanks!