[unrev-II] Multiple Parents, Slash and Backslash

From: Eric Armstrong (eric.armstrong@eng.sun.com)
Date: Tue Jan 02 2001 - 14:29:41 PST

  • Next message: Garold L. Johnson: "RE: [unrev-II] Multiple Parents, Slash and Backslash"

    In conversation with Eugene, he's been asking
    the question: Are multiple parents for a node
    really necessary? Basically, if that concept
    adds complexity, maybe we should plan on not
    implementing it.

    I have felt that it was vital, but so far have
    not presented a compelling enough use case to
    settle the argument. This message is an attempt
    to do so. (And it led to another interesting
    insight that prompted me to jot down my thoughts.)

    MESSAGING BASIS FOR SYSTEM
    --------------------------
    I take it as a given that I want to interact
    with the system in much the same fashion that I
    interact with my email client -- only with much
    more powerful capabilities. To me, the interchange
    of messages is the right way to think about
    designing a "front end" that captures knowledge
    organically.

    The basic problem with knowledge-storage systems
    in general as that they are too inflexible, and
    extremely difficult to right. Even when they do
    sometimes get it right, the lack of flexibility
    makes them less right over time, until they
    eventually become useless. (John Lowrance at SRI
    has some interesting war stories on the subject
    that illustrate the point.)

    So, the "email paradigm" is, to me, a given. The
    system must allow users and the system to
    interact. A user should be able to send a query
    and get the system's idea of a response. Other
    users should be able to review that response and
    refine it, if necessary. In the process, they
    should be making the system smarter, so it can
    do a better job of generating answers in the
    future (possibly by interacting with the originator
    of the message, before the message is actually
    sent).

    MULTIPLE PARENTS
    ----------------
    Thinking of the system as an "interactive, message-
    based, knowledge repository" (IMKR?) leads to one
    motivation for allowing a node to have multiple
    parents: the drafts folder.

    In my email system, I have a drafts folder that
    keeps copies of messages I am working on. I
    frequently use it to keep todo lists for various
    projects I am working on. (I create the message,
    but don't send it. I check things off as they're
    complete, and occasionally send copies of the
    message as a status report.)

    That is a useful facility. But note that my draft
    of things to do is in a different folder from the
    project folder, where I have filed the various
    messages and information tidbits that tell me how
    to DO those tasks.

    Now, it would be excellent if the todo list
    contained links to those messages. We know we want
    that. But it would also be useful if the todo list
    itself could have dual membership, so that it
    simultaneously exists in the Drafts folder and in
    the folder for the project it applies to.

    Looking in the Drafts folder would then show me
    all the todo lists for every project I'm working
    on. Looking in a given project would give me the
    information relevant to that project, along with
    the todo list. There is just no substitute for
    having that todo list belonging to two folders!

    SLASH and BACKSLASH
    -------------------
    Thinking of a message with dual membership led me
    to an interesting question: How do you distinguish
    messages that have the same title, though they
    reside in different folders? How should they appear
    in the Drafts folder, in other words, so it is
    clear which one is which?

    For example, suppose that Project A has a "ToDo"
    message, and Project B has a "ToDo" message. How
    do they appear in the Drafts folder? Clearly, the
    system would need to add the folder information.
    In other words, it should add as much parentage
    information as necessary to distinguish two
    otherwise equivalent messages.

    It flashed on me then that here was a *perfect*
    place to use the backslash. The Drafts folder
    might then look like this:
      Drafts
        Questions
        ToDo\Project A
        ToDo\Project B

    Of course, it should also be possible to put the
    parent information on the left, and revert to
    forward slashes. That would change the sort,
    producing:
      Drafts
        Project A/ToDo
        Project B/ToDo
        Questions

    Anyway, them's my thoughts for the day...

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