Re: [unrev-II] Versioning Discussion

From: Paul Fernhout (
Date: Fri Oct 27 2000 - 18:52:00 PDT

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    Eric Armstrong wrote:
    > The thing I notice immediately is the distinction between contents and
    > subnodes. It appears I am not alone in realizing these two conceptual
    > entities must be kept distinct. Yes?

    Yes. It would seem one needs to distinguish the conceptual "thing" to be
    versioned from the "versions" themselves. So, the thing to be versioned
    then acquires some list of historical versions of contents.

    One weak analogy might be is almost as if one has a class (subnode) and
    instances (versions of contents). One violation of this class-instance
    analogy is that in theory (but probably not practice) you might allow a
    contents node to be under multiple subnodes (e.g. imagine for example a
    function that was identical in two Java classes and you fixed it in one
    place and wanted to use the identical version in another place by just
    referencing the first rather than copying it).

    This notion of "thingness" (or subnode in this case) of what is
    referenced is in some sense separate from the notion of "version" of the
    thing, where a "version" is a particular set of contents.

    This "thingness" idea as it relates to ancestral versions becomes a
    complex issue when one starts to think about how subnodes (things) might
    merge or split to become new sets of version history (new derived
    things). This might be important in tracking the history of the changes
    (contents) for an idea (subnode) such as if one makes a copy of a
    subnode. For now I ignore that in the Squeak file archiver example --
    you can't specify that a file is the merger of two or more specific
    versions of other files for example. Yet, that information regarding
    origin of content might be useful to know. Similarly the system doesn't
    track if a file is split into two parts, each part pointing back to the
    whole subnode it was derived from. All things to add...

    -Paul Fernhout
    Kurtz-Fernhout Software
    Developers of custom software and educational simulations
    Creators of the Garden with Insight(TM) garden simulator

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