[DAS] Feature-by-target in DAS 1.5x?

[Thomas Down]

Hi Lincoln,

I'm just looking at DAS1.5 support for Dazzle, and was wondering
if you'd thought any more about the feature-by-target fetching
we discussed last week.

Now that you can request features by feature-ID and group-ID
as well as segment-ID, target-ID seems a logical addition to
complete the set.

The use case I have in mind for this is:

  1. Client issues a feature-by-ID request to some server (not
    necessarily the reference server).  For instance, the user
    may have requested a particular (well-known) feature from
    a server offering matrix attachment site annotations.

  2. The annotation server responds with the requested feature,
    attached to the appropriate segment -- in this case, a clone.

  3. The client checks the segment ID against the top-level
    entry points list from the reference server, and notices
    it's not there.

  4. The client issues a request like:

        das/reference_server/features?category=component;target_id=AL121903

    and receives information about where that particular clone
    is mapped into the assembly.

  5. If it's a multi-layer assembly, the client might have to
    repeat step 4 to navigate to the top level coordinate system.

  6. The client is now aware of the position of the requested
    feature within the assembly, and can present the user with
    an approrpriate display of the region around the requested
    feature.


Does this make sense?  From a server-developer's point of view,
I'd argue that a feature-by-target function is easier (and makes
a lot more sense) to implement that the `supercomponents' scheme.
It's also more explicit what's going on from a client's point of
view.


What do you think about this?

    Thomas.