events vs callbacks (was Re: SAX2 (was Re: DOM vs. SAX??? Nah. ))

Bill la Forge b.laforge at
Thu Feb 25 17:16:20 GMT 1999

>Event-based programming existed before people started encapsulating
>events in structures or objects.  I'd define SAX as an event-based API 
>that reports events using callbacks.

But why are we not taking advantage of having the events as objects?
I've tried to second guess why this is so, but I think the arguments in
favor of object-based events is stronger: the added overhead is balanced
by greater simplicity and subsequently less overhead in other areas; the
added flexability adding additional utility to all conformant code.

Take for example the DOMParser. It subclasses InputSource to play some tricks.
And because InputSource is an object, this lets us use DOMParser with 
filters that never ever considered having InputSource be anything other than
what was provided with SAX.

The same will be true of SAX2, if events are objects. It will dramatically increase
the utility of all the conformant code!


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