in reply to Make Current State Known

I'd use something like IPC::DirQueue to let tasks put jobs for other tasks in there.

E.g., if the coffee task is halfway through, it could put a 'make toast' job in there for the toast to get started.

Replies are listed 'Best First'.
Re^2: Make Current State Known
by GrandFather (Saint) on Feb 10, 2006 at 21:20 UTC

    Feed forward systems like that depend on the coffee app knowing about the toast app and its constraints - you end up with everything having to know about everything.

    If the apps simply publish their current status other apps in the know can find out what they need to know without the publishing app having to know anything about the subscriber app.

    DWIM is Perl's answer to Gödel
[reply]
      Feed forward systems like that depend on the coffee app knowing about the toast app and its constraints - you end up with everything having to know about everything.
      Either
      • the coffee task knows about the toast task or
      • the toast task knows about the coffee task or
      • a centralized manager knows about both the coffee and the toast task.
      Which one is the easiest/best maintainable implementation depends on the nature of the application.
[reply]

        With publisher/subscriber the toaster need only know to check the RequiredForBreakfast and TimeToCompletion attributes in the other app attributes files. It doesn't need to know anything at all else about the other apps and the other apps don't need to know about the toaster.

        When the porridge app is added both the coffe app and the toast app can adjust their timing without any code changes because they both check for the same attributes of other apps without regard to what those apps are.

        DWIM is Perl's answer to Gödel
[reply]

In Section Seekers of Perl Wisdom