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definition of the term transform/transformation

From: gregory j. rosmaita <oedipus@hicom.net>
Date: Wed, 9 Jun 1999 15:06:44 -0400 (EDT)
To: Authoring Tools WG <w3c-wai-au@w3.org>
cc: Unagi San <unagi69@concentric.net>
Message-ID: <Pine.BSI.3.95.990609143925.27835A-100000@ns.hicom.net>
aloha, all!

According to the agenda for today's meeting, I was tasked with a second 
action item during the course of the 2 June meeting: to define the term 
"transformation", which Wendy Chisholm used in her tersification of 
Guideline 2.3.4:

	"Preserve all accessibility content during transformations
	and conversions"

Yet, as Jim Allen pointed out, the term recurs in Guideline 2.6.6

	"Allow the author to perform tag transformations. For example, 
	to transform visually formatted elements to structure elements, 
	or tables to lists."

The question, therefore, which has been plaguing me for the past week is:
"Are we using a single term to describe two different phenomena?"

I was tasked with defining "transformations" during the 2 June meeting
because I had raised an objection to the use of an undefined term,
"transformation", in our document which is used to describe a technical
process in another W3C Working Draft: that for the Extensible Style Sheet
Language (XSL), version 1.0
	<http://www.w3c.org/TR/1998/WD-xsl-19981216.html>

If we are to use the terms "transform" and "transformation" in the
Authoring Tool Guidelines, therefore, we should first examine how the
terms "transformation" and "transform" are utilized in the XSL WD.  Such
an examination is necessitated by the fact that the term is _NOT_ defined
in the XSL WD. 

The first instance of the term occurs in the XSL WD's Abstract, which I 
quote in full below:

[begin first quote]
	XSL is a language for expressing stylesheets. It consists of two
	parts:

		1. a language for transforming XML documents, and
		2. an XML vocabulary for specifying formatting semantics. 

	An XSL stylesheet specifies the presentation of a class of XML 
	documents by describing how an instance of the class is transformed 
	into an XML document that uses the formatting vocabulary."
[end first quote]

The second example is drawn from the fourth paragraph of the XSL WD's Overview:

[begin second quote]
	XSL does not require result trees to use the formatting vocabulary 
	and thus can be used for general XML transformations. For example, 
	XSL can be used to transform XML to "well-formed" HTML, that is, 
	XML that uses the element types and attributes defined by HTML.
[end second quote]

The next two examples are more technical in orientation.  The third quote
is drawn from the second paragraph of section 3.2.3, which is entitled
"Display-spaces": 

[begin third quote]
	A display-space between two areas (block or line) is specified by 
	a triple of values (minimum, optimum, maximum) which defines the 
	limits of how the space may be transformed by later processes such 
	as vertical justification.
[end third quote]

The fourth quote is from section 3.2.4, which is entitled "Inline-spaces":

[begin fourth quote]
	An inline-space is specified by a triple of values (minimum, 
	optimum, maximum) which defines the limits of how the space may be
	transformed by later processes such as justification. It separates 
	inline-areas in a direct analogy to the way display-space separates
	block-areas.
[end fourth quote]

Clearly, when the terms "transform" and "transformation" are used in the
XSL WD they are being used to describe processes whereby one object is
changed, according to a discrete set of rules, into another object.  Such
an understanding of the terms can also be applied to the 2 instances of
the term "transformation" which appear in the Authoring Tool Guidelines. 

However, I still have questions in my mind as to what exactly we are
attempting to express through the use of the term "transformations" in
Guideline 2.3.4.  The term "conversion" is clearly defined in the
Authoring Tool Guidelines "Terms and Definitions": 

[begin quote]
	Conversion Tool 
		A Conversion Tool is any application or application feature 
		that allows content in some other format (proprietary or 
		not) to be converted automatically into a particular markup 
		language. This includes software whose primary function is 
		to convert documents to a particular markup language as well
		as "save as HTML" (or other markup language) features in 
		non-markup applications
[end quote]

In light of this definition, the only possible definition of the term 
"transformation" that I have been able to formulate in the past week is:

[begin first proposed definition]
	Transformation Tool
		A Transformation Tool is any application or application 
		feature that allows content which is marked up in a 
		particular markup language to be transformed into another 
		markup language.  This includes software which allows the 
		author to change the DTD defined for the original document 
		to another DTD.
[end first proposed definition]
		
Admittedly, this isn't the most elegant of definitions, but then again,
neither is the definition of "Conversion Tool", which uses the word
"convert" as part of the definition (an example I reluctantly followed). 

A more serious problem with the above definition is that it doesn't cover
the use of the term "transformation" which occurs in Guideline 2.6.6

[begin text of GL 2.6.6]
	Allow the author to perform tag transformations. For example, 
	to transform visually formatted elements to structure elements, 
	or tables to lists.
[end text of GL 2.6.6]

Given this, I, personally, would prefer that the AU GL use a broader
definition of the term "transformation", to wit: 

[begin second proposed definition]
	Transformation
		A process whereby one object is changed, according to a 
		discrete set of rules, into another, equivalent, object.
[end second proposed definition]

Which brings me to the following conclusion:  perhaps we need both
definitions.  Therefore, let me take one last stab at a unified
definition:

[begin third proposed definition]
	Transformation
		A process whereby one object is changed, according to a 
		discrete set of rules, into another, equivalent, object. 
		This includes any application or application feature that
		allows content which is marked up in a particular markup 
		language to be transformed into another markup language, 
		such as software which allows the author to change the DTD 
		defined for the original document to another DTD. It also 
		describes the substitution of textual equivalents for 
		graphical or visually defined elements and objects.
[end third proposed definition]

Clunky, I know, but as comprehensive as I could manage...

One last note--since I am still experiencing connectivity problems, please
CC any responses to my <unagi69@concentric.net> eddress, which is included
in this emessage's CC field.

Gregory.
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Received on Wednesday, 9 June 1999 15:14:10 UTC

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