Re: DD: ports -Reply

Subject: Re: DD: ports -Reply
From: "Mitch C. Amiano" <amiamc@xxxxxxxxxxxxxxx>
Date: Wed, 06 Aug 1997 09:14:29 -0400
I'd been keeping some notes for myself, but decided to post them here
after seeing the insufficient response to the question of "what are
ports."  I'd submit them for the glossary, but can't find the DTD for
glossary entries which was posted earlier. 

Anyway, what do the experts think:

Atomic flow object

Atomic flow objects are flow objects which do not have ports, because
they do not relate other flow objects together. Atomic flow objects are
flow object which are terminal with respect to a given branch in a flow
object tree. Contrast this to a flow object which is non-atomic.

Flow Object

An object which implicitly (via the class name) or explicitly (through
attributes) contains formatting requirements as well as the document
instance data which are required to achieve the formatting. Non-atomic
flow objects use the Principle Port or named ports to attach to a stream
of contents, while atomic flow objects are self contained.


A port is connection to a stream of flow objects. The stream represents
a list of contents of the flow object which has the port. The role of
the stream thus connected is presumably subservient, subordinate,
prepositional, etc., with respect to the flow object which has the port.
Flow objects in DSSSL order themselves by reference to one another, in a
flow object tree. This collection is abstracted as a list (called a
"stream"), and the flow-object datum that gets you access to this list
is called a Port.
Non-atomic flow objects have a Principal Port, and may also have one or
more Named Ports. 

Principal Port

A port on a (non-atomic) flow object which points to the primary
content. As with all ports, the content is a stream of flow objects.
Many flow objects will need to have a port, because they relate other
formatting objects together in some way. DSSSL provides a default port
called the Principal Port, to which contained flow objects will be
connected unless otherwise specified. (Contrast these flow objects to
atomic flow objects).

Named Port

A port on a (non-atomic) flow object, other than the principal port,
which points to content and to which a name has been assigned. As with
all ports, the content is a stream of flow objects.
Named ports supplement the principle port by providing a connection
point for alternative, additional, or parallel representations of the
content of a given flow object.

Sebastian Rahtz wrote:
>  > Probably a very simple explanation Sebastian,
>  > Port is the opposite of starboard isn't it?
> no, its a fortified wine from Northern Portugal....
>  > We (the beginners) need to be told it _needs_ to be
>  > in DD before it gets included.
> ...
>  > Which chapter please?
>  > _and_ could / would you author it?
> it belongs at the same level as `what is a flow object', i think. in
> fact, its part of `what is a flow object'.
> i wish i _could_ author it. i am afraid ports baffle me. i would not
> even have met them, were it for having to do math. thus when i come
> to process my <FR> (fraction) element, I do
> (element fr
>  (make fraction
>    (process-children-trim)
>  )
> )
> (element nu
>       (make math-sequence
>          label: 'numerator
>    (process-children-trim)
> ))
> (element de
>       (make math-sequence
>          label: 'denominator
>    (process-children-trim)
> ))
> ie the <DE> and <NU> rules attach themselves like leeches to the
> fraction FO I created for <FR> (the fraction FO has predefined ports
> called numerator and denominator)
> so i know what to do empirically, but i don't think this a rational
> explanation of what problems ports[1] solve
> Sebastian
> [1] apart from being good places to dock ships, of course
>  DSSSList info and archive:

Mitch C. Amiano                                        
Technical Staff Member  Advanced Design Process Group  Alcatel Network
Opinions expressed are my own and are not a representation of Alcatel

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