Al,
I think what you are looking for comes out of this para in 1808:
The base URL of a document can be established in one of four ways,
listed below in order of precedence. The order of precedence can be
thought of in terms of layers, where the innermost defined base URL
has the highest precedence. This can be visualized graphically as:
.----------------------------------------------------------.
| .----------------------------------------------------. |
| | .----------------------------------------------. | |
| | | .----------------------------------------. | | |
| | | | (3.1) Base URL embedded in the | | | |
| | | | document's content | | | |
| | | `----------------------------------------' | | |
| | | (3.2) Base URL of the encapsulating entity | | |
| | | (message, document, or none). | | |
| | `----------------------------------------------' | |
| | (3.3) URL used to retrieve the entity | |
| `----------------------------------------------------' |
| (3.4) Base URL = "" (undefined) |
`----------------------------------------------------------'
What we are now talking about is how to define the base URL of a
message entity.
I think the default base URL should be the MID, and the only meaningful
relative URLs should be in CID format; you'd have to invoke some naming
mechanism to get any other kind of relative URL to work, either by
designating the base according to (3.1) above or by another scheme
like the suggested "content-disposition:" stuff.
This argues strongly for a "mid:xyzy(_at_)wawa(_dot_)com/cid:wwww@ixi.org"
format
- using slashes to separate the components.
Harald A