Re: XML/SGML

["Russ W. Urquhart" urqurw@xxxxxxxx]

On Thu, Jul 29, 1999 at 03:54:25PM -0500, Harrison, Shawn wrote:
> Russ said:
> Any
> display/printing concerns were left to DISSYL (sp?) i believe.
> ...
>
> DSSSL.

I knew i'd get the name wrong. :)

>
> ...
> While i like the
> notion of an ascii-based markup, i would think or i would want my
> wordprocessor
> to be able to have some control over the actual layout portions of my
> document,
> in a precise manner. That includes, but not limited to, font size, paper
> size,
> leading, precise graphic placement, etc.
> ...
>
> Right, you're exactly right. You *do* want to control the layout for the
> document. What the designers of SGML noticed is that distinctions in
> appearance between various elements of the document correlates very
> closely with the structure of the document. For instance, headings look
> different from titles which look different from body text, because they
> are structurally different parts of the document. So, rather than having
> the mark-up in the document itself reflect the *appearance* of the
> elements, the mark-up would reflect the *function*. Form follows
> function. As a result, if you want to change the appearance of every,
> say, heading, you can do so knowing that you're not also affecting
> unrelated elements.
>
> In such a system, you gain control of the actual appearance of the
> document in one of two ways: (1) you create a stylesheet which defines
> the appearance for each structural element; and/or (2) you put attributes
> into the structural tags to describe the appearance of that element. An
> example of the first approach would be to define somewhere else (in the
> stylesheet) that 
First-Level Heading
 should be Optima Bold 14pt.
> An example of the second approach would be like this: 
 weight="Bold" size="14pt">First-Level Heading
. The first approach
> keeps the appearance information separate from the document, while the
> second approach includes it but retains a structural approach to mark-up.
>

I'm familiar with all this, and i think that it makes sense. My question, and
maybe you can answer this, is where is the stylesheet defined? This sort of
layout was used in Ventura, (and a very flexible construct i thought). You
created, in the course of defining your various tags, the layout of the page
itself. This was stored in the stylesheet. This actually controlled how the
document looked. The text was safe in another file.


> ...
> The capabilities to do some of these
> things in HTML is kind of kludgy IMO and suggests limited capabilites in
> HTML
> to display these attributes. As i've said, i haven't yet gotten into XML,
> but,
> i would want to be able to control these things in my
> wordprocessor/publishing
> system. If later, i could then output this to XML, for someone else's
> benefit,
> that would be fine.
> ...
>
> XyWrite styles can control these things to a limited extent. Let me give
> you another example of how such a thing might work in a word processing
> tool. I'm tinkering with a programming language called Tcl/Tk, which
> includes a very good rich-text function (Tcl is the programming language,
> Tk is the GUI ToolKit). The language has a tagging method very similar to
> that used by, say, XML. For instance, if I want text to be tagged with a
> "h1" tag, I issue a command something like the following:
>
> 	.text tag add "h1" sel.first sel.last
>
> "sel.first" is the beginning of the selection (func DB), and "sel.last"
> is the end (func DE).
>
> Then, I can issue a command like the following:
>
> 	.text tag configure "h1" -font "Optima 14 Bold"
>
> The point is this: the structural tagging of the document is kept
> separate from the "configuration" (appearance) of the tags, but I can
> certainly control the appearance of the tags. I can also program the
> system to handle this information in either way described above: I can
> have the tag configuration information saved separately in a stylesheet,
> or I can have that information saved as attributes in the tags.
> Furthermore, Tcl/Tk operates exactly in the way you described: when tags
> are "stacked" on top of each other (for instance, a "bold" tag within a
> "h1" tag), each tag is assigned a priority level, and the tag with the
> higher priority modifies the configuration of the text, but only for the
> attributes that it defines -- other attributes are left alone. For
> instance, if I DEFINED (DF) part of the "h1" text above and issued the
> following commands:
>
> 	.text tag add "remove" sel.first sel.last
> 	.text tag configure "remove" -strikethrough yes
>
> The result would be that the selected text would have a line through it,
> and would still be 14pt Optima Bold. And the surrounding text would be
> unchanged, 14pt Optima Bold without a strikethrough. Tcl/Tk handles this
> in a way that is completely analogous to ... -- the tag is
> turned on, then turned off, without affecting other surrounding text and
> its attributes.
>

This i understand and agree with. I'm just curious as to when and where I, as
the author, would go about defining the stylesheet?

The other question that comes to mind is that if the stylesheet is totally
removed from the document, and an H1 tag only means that an H1 is here,
according to you and Leslie, it would seem that i would either have to make
sure that everyone i send stuff to has my DTD's or that i use some other well
used DTD's, is that correct?


> ...
> For whatever reason, when i tried to get Xywrite's styles to do this, i
> couldn't get it to work that way. As i said earlier, this is more than
> likely
> pilot error on my part,
> ...
>
> Don't sell yourself short. XyWrite has inherent limitations in this area.
> Rather than turning a tag "on" and then "off", it turns a style or a mode
> "on" until another style or mode intervenes to replace it.


This was exactly my experience!



 So, for
> instance, ≪USh1≫ will continue in effect until another style
> intervenes, such as ≪USbody≫. There is no built-in XyWrite mechanism
> for ≪endUSh1≫ or something like that, without starting another style.
> (The command ≪PS≫ uses the "previous style", but this appears to mean
> the previous style in the order listed on the stylesheet -- not the one
> that was in effect before the current ≪US...≫ was invoked. The use of
> ≪NS≫ and ≪PS≫ depends on the order of elements in the stylesheet
> rather the order in which elements are invoked. Bother! If only. . . .)
> (You *can* get "modes" to function in a "on" and "off" way if you use,
> i.e., ≪md+bo≫ ... ≪md-bo≫. I believe all of the MD commands in
> XyWrite are capable of functioning in this way. But not the styles. It'd
> be nice if you could ≪US+h1≫ ... ≪US-h1≫. That would do it! But
> alas.)
>

Well, i feel a little better now!


Thanks


Russ