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From: wjh+@ANDREW.CMU.EDU (Fred Hansen)
Newsgroups: comp.soft-sys.andrew
Subject: Re: Writing data graphs
Message-ID: <sYQNKj_00VsPQou2VQ@andrew.cmu.edu>
Date: 17 May 89 15:54:23 GMT
References: <8905160257.AA02325@bullwinkle.cs.uiuc.edu>
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> Excerpts from ext.in.info-andrew: 15-May-89 Writing data graphs Gregory
> Rogers@a.cs.uiuc (1189)

> The file would be something like this:

> 	\begindata{aclass,1}
> 	\begindata{bclass,2}
> 	\begindata{dclass,3}
> 	... d stuff
> 	\enddata{dclass,3}
> 	... other b stuff
> 	\enddata{bclass,2}
> 	\begindata{cclass,4}
> 	\a_reference_to_an_object_that_has_already_been_filed{dclass,3}
> 	... other c stuff
> 	\enddata{cclass,4}
> 	... other a stuff
> 	\enddata{aclass,1}

> What should I do with
> "a_reference_to_an_object_that_has_already_been_filed"?

There is an answer to this question in theATK architecture:  Both B and
C should refer to their embedded object by the dataobject identifier.

If you look at a text data stream, you will find something like

    \view{sliderv,270125020,2,0,0}

which says that at this point in the image a view object of class
sliderv should be instantiated looking at data object 270125020.  (The 2
is an identifier of this view in the view stream.  The 0,0 indicates
that the size is not explicit;  if the size were explicitly set by the
user these values would be non-zero.)

If another view is to examine the same data object, it would appear as:
    \view{bargrphv,270125020,3,0,0}

(This and the preceding example are taken from Nathaniel's post about
this same topic.)


When text encounters a data object in its incoming stream, it does
nothing except put it in the dictionary.   {See
andrew/atk/text/text.c:text__HandleKeyword:(strcmp(keyword, "view") ==
0).}  The \view data stream item finds the data object in the dictionary
and displays it with the view.  {See
andrew/atk/text/textv.c:CreateMatte.}

In future, it is possible that an ATK data stream will be a sequence of
data objects, some of which will have references to others.




Fred Hansen

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