[Usability]Mime type to application associations.

[Mathew Johnston <johnston capsaicin ca>]

I'm really having trouble understanding the mime type to application
association scheme that Gnome uses. This is a major usability issue for
me.

First, I'll give my expectations.

A file has a content type; the type may be a mime type (example,
"application/x-dia-diagram") or gnome type category (example,
"Documents/Diagram/Dia diagram"). Whatever it is, it is a classification
of what type a file is. Type could be determined through magic numbers,
extention, or some information provided through protocol (HTTP
Content-type header, extended filesystem information, etc). 

Content types would either point to applications or applications would
point to content types.  Associations between apps and types would be
many to many. I think that applications pointing to content types makes
more sense; it's more managable too.

Right now, I don't know how in the hell all of these applications get
associated with my file types and I have no way of controling it (how
did gedit, NEdit, vi, etc all get associated with Plain text type
files?)

Here's my vision:

Applications would be defined and registered centrally; this
registration could be used to populate menus, etc. An interface would be
provided to manually register applications, easily (for non compliant
apps or for scripts). Compliant applications would register upon
execution, if they are not already registered. The application would
also mention to the system which file types it is capable of dealing
with as well as how it is capable of dealing with the types (view, edit,
compress, uncompress, etc); types would be referenced by pattern, so
that an application could say, "I can compress any file", or, "I can
edit any text file". Users should also be able to add extra types for an
application to support. One application and action could be associated
with a specific type as the default action (for double clicking). 

Does that not make sense? This would also be fairly straight forward to
implement from an interface perspective and it should be easy to explain
to new users (you install a new app that knows that it can do certain
things with certain file types and then the system picks up on that and
makes it easy for you to get to the apps).

Thanks,
Mat.