DEBS08(5) - Event-based Constraints


 
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Old 07-07-2008
DEBS08(5) - Event-based Constraints

vincent
Mon, 07 Jul 2008 12:41:24 +0000
Another paper at the Distributed Event Based Systems conference was on “Event Based Constraints for SensorNet Programming”. I had high hopes for an interesting paper on goal-driven CEP, but in fact the authors (from Brown University, USA) seemed to define “constraint” as a synonym of “filter” (as in “temporal, spatial, attribute-based or existential constraints on some event”). So there was no CLP-type relaxing of constraints during event processing to try and achieve some goal.
The paper did describe some an interesting approach to distributed CEP, using spatial and temporal event processing elements to divide up a high-datarate environment (detecting people being chased in a crowd). The main problem was, as always in distributed event processing (without a shared memory bus), ensuring that all possible event correlations can take place (with the right event being in the right processor at the right time). Probably for some sensor processing, though, a 100% success rate is not a requirement (i.e. if someone runs across an “event process boundary”, they will be presumably be picked up by the next event processor at some point).
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SDL::Event(3)						User Contributed Perl Documentation					     SDL::Event(3)

NAME
SDL::Event - a SDL perl extension SYNOPSIS
use SDL::Event; my $event = new SDL::Event; # create a new event $event->pump(); # pump all events from SDL Event Queue $event->poll(); # Get the top one from the queue while ($event->wait()) { my $type = $event->type(); # get event type # ... handle event exit if $type == SDL_QUIT; } DESCRIPTION
"SDL::Event" offers an object-oriented approach to SDL events. By creating an instance of SDL::Event via new() you can wait for events, and then determine the type of the event and take an appropriate action. EXAMPLE
Here is an example of a simple event handler loop routine. See also SDL::App::loop. sub loop { my ($self,$href) = @_; my $event = new SDL::Event; while ( $event->wait() ) { # ... insert here your event handling like: if ( ref($$href{$event->type()}) eq "CODE" ) { &{$$href{$event->type()}}($event); $self->sync(); } } } METHODS
new() Create a new event object. type() Returns the type of the event, see list of exported symbols for which are available. pump() poll() wait() Waits for an event end returns then. Always returns true. set( type, state ) Set the state for all events of the given event's type set_unicode( toggle ) Toggle unicode on the event. set_key_repeat( delay, interval) Sets the delay and intervall of the key repeat rate (e.g. when a user holds down a key on the keyboard). active_gain() active_state() key_state() key_sym() key_name() key_mod() key_unicode() key_scancode() motion_state() motion_x() Returns the motion of the mouse in X direction as an absolute value. motion_y() Returns the motion of the mouse in Y direction as an absolute value. motion_xrel() Returns the motion of the mouse in X direction as a relative value. motion_yrel() Returns the motion of the mouse in Y direction as a relative value. button_state() Returns the state of the mouse buttons. button_x() button_y() button() AUTHOR
David J. Goehrig Documentation by Tels <http://bloodgate.com/> SEE ALSO
perl SDL::App perl v5.12.1 2010-07-05 SDL::Event(3)