[e-lang] Two-vat figure

Karp, Alan H alan.karp at hp.com
Tue Jun 21 11:08:19 EDT 2005

Ping wrote:
>     1.  The diagram is rearranged to read mostly left to right,
>         of bottom-right to bottom-left to top-right.  Reasoning:
>         left-to-right reading order is more natural.

But with the arrows pointing to the right, it's not clear what the
sequence is.  My first reaction was that the little boxes in the bottom
row move to the right.  Perhaps some sort of labeling in the arrows
would help.  S1, S2, ..., Q1, Q2, ..., but then you lose the "33" in the
queue in the display vat.  I don't know what the right answer is, but I
bet it involves a detailed caption.
>     3.  The vats and objects are given non-cryptic names.  Reasoning:
>         words are easier to understand than abbreviations like XL.
>         (Mark, i know you said you preferred not to do this.  We can
>         change it back if you want, but i wanted to at least show what
>         i originally had in mind.)

I think these names make the example easier to understand.

>     6.  Dotted arrows are added to show the eventual message being
>         placed on the queue and removed from the queue for processing.
>         Reasoning: without these arrows, it looks like the message is
>         being delivered immediately.  The arrows also make it clear
>         that the message arriving, the message on the queue, and the
>         message being delivered are one and the same message.  (In
>         the original there is no clear cue that the message on the
>         queue is the message on the incoming pointer.)

But it looks like the eventual send is resolved off the tail of the
queue, when it's really off the head of the stack.  I don't know how to
resolve this problem without using more figures.

> These 1-vat and 2-vat figures shade the stack and queue areas of the
> vat.  If it's really necessary for Springer the shading could be
> removed and replaced with partition lines, but shading is a better
> option when possible since the extra lines generate unnecessary visual
> clutter and line crossings.

You could also outline them with dashed lines, even labeling them
"immediate stack" and "eventual queue".
> -- ?!ng
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Alan Karp
Principal Scientist
Virus Safe Computing Initiative
Hewlett-Packard Laboratories
1501 Page Mill Road
Palo Alto, CA 94304
(650) 857-3967, fax (650) 857-7029
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