Event Delivery Abstractions for Mobile Computing

B.R. Badrinath and Girish Welling, Rutgers DATAMAN

One-line summary: Distinguishes monitored events (poll for parameter of interest to leave specified window) from triggered events (low-level state change, i.e. insert PC card), and defines a language-level mechanism based on C++ objects for event registration, delivery, and handling.

Overview/Main Points

Each app may define several EventObjects or MonitorObjects (by subclassing from base classes) that register interest in specific events. Event is delivered once to each registered object.
Small amount of data is piggybacked onto event delivery. Not clear how to provide substantially more data, esp. since event handlers are encapsulated objects.
Central Event Registrar provides low-level event capture and encapsulates them for delivery. OS-specific peculiarities of dealing with events are encapsulated here.

Relevance

Proposes a standard abstraction for event delivery; potentially many uses for this model (interactive groupware, network events, mobility awareness, etc.)

Flaws

Implementation is in Mach 3.0; makes use of Mach threads (for monitor objects) and Mach objects, and C++ class mechanism for creating objects. I.e. all the hard work is really already done in the OS. Not appropriate for portables.
Future work includes determining what minimal OS functionality is necessary to support their abstraction. In my view, this is the interesting question, and the one I expected the paper to answer.
Future work includes abstractions for object and thread migration. Not clear what the relationship is to this paper, or whether they will again punt to the OS and just encapsulate the OS-provided behavior in a class. I mean, anyone can do that.

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