Clipboards + Meaning

Thomas M. Farrelly s720@ii.uib.no
Wed, 10 Dec 1997 10:29:02 +0100


David E. Manifold wrote:
> 

[...]

> The
> implementation is independent of meaning, so data can be stored in any
> format, but it still has the same outward, semantic appearance which is
> its meaning.
> 

But in practice, the 'semantic appearance' must be implemented. So
eventually programmers must resort to 'formats', if they don't want to
invent their own wheels.

For example, every object both provides and uses formats, in the form of
interfaces.

And also, every format must be formally specified somewhere in the
system, eighter statically or dynamically. As I understand, you want to
specify formats/interfaces/semantic appearence dynamically, i.e. using
dynamic linking and late typing, and so, you need to specify such a
dynamic system, which in its turn will need to be statically specified.

By static specification, I mean using constant relative addressing. For
example, if I have a string of characters, a label, and a pointer to
some object assosiated with the string, I could define my format like
this:

	byte	00	01	02	03	04	05	06	07
		\_____string pointer_____/      \_____object pointer ____/

Where the string pointer would have offset 00 and the object pointer
would be 04.

I could call this little format for 'a reference', for example, and use
it to build a new dynamic format, like 'picture'.

picture
  list of recerences
	bitmap, pointer_to_bitmap
	pallette, pointer_to_pallette

'picture' is an example of a simple dynamic format. The reason it is
dynamic, is that you consult the data for the path to further data, thus
the paths through such structures may change dynamically. But there is
no magic to this changability or adaptability. It is all accounted for
on the lower abstraction levels ( or in your case, the meta-objects form
here to n ).



--
 ____________[ Thomas M. Farrelly ]_____________
 http://ii.uib.no/~s720/   mailto:s720@ii.uib.no