> well, what about iframe as a kind of object, for implementor?
> http://www.w3.org/TR/REC-html40/present/frames.html#h-16.5 
> mentions that IFRAME and OBJECT are 'similar'.

No, this means that the kind of insertion is similar, not the elements
themselves, correct me if I am wrong. The kind of use is definitely different, you
use the iframe element for a (in my point of view) poor and unnecessary
frame integration, and the object element to embed multimedia, like Flash movies,
images, etc. As a matter of course, you can use the object element within an
iframe.

> does it mean IFRAME is a kind of OBJECT, which inherit OBJECT?
> (I know that DOM Level 2 HTML specify HTMLIFrame as child of HTMLElement:
> http://www.w3.org/TR/DOM-Level-2-HTML/html.html#ID-50708718 )

No... they are IMHO independent from each other, there is no relation
between them... see text above.

> I'm willing to implement all the non-trivial datas: APPLET, IMG, EMBED,
> and IFRAME (if possible), as a kind of OBJECT.
> is this reasonable?

As far as I know it is recommended to use the object element for (all)
multimedia integration... Me, I recommend to use the img element for images
(although you can use the object element for this, too), object elements for
alternative multimedia, and to pass on the iframe element.


Regards,
 Jens Meiert.



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