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An architectural issue

From: Steve Zilles <szilles@adobe.com>
Date: Wed, 08 May 2002 20:41:38 -0700
Message-Id: <5.1.0.14.2.20020507180014.0431bbb8@mailsj-v1>
To: www-tag@w3.org
I believe that the handling of formatting properties across W3C (document 
format) specifications needs an architectural principle or finding.

Formatting properties are the properties that various document formats 
(HTML, XML, SVG, SMIL, MathML, ...) use to control the styling of the 
content of the format for some presentation medium, such as display 
screens, audio systems or printed page.

For an illustrative example that shows the architectural problem, consider 
embedding an XHTML/XML chunk within an SVG chunk within an XHTML/XML 
document.  Further, assume that the XHTML/XML pieces are styled either with 
CSS or XSL. Typically, the author (and the reader) would want consistent 
styling for all three pieces. For the styling to be consistent, both SVG 
and CSS/XSL must use the same properties for the same purpose. In addition 
to using the same properties, the interpretation of those properties must 
be the same in both SVG and in CSS/XSL (or one or the other piece may have 
no understanding of the property).

The implication of this example is that there is an architectural principle 
that needs stating. Much as the W3C has said, "whenever you are creating a 
file format, you must give a very strong reason for using something other 
than XML as the basis of the syntax of the format", there should be an 
architectural principle that says, "whenever you are about to create a new 
formatting property, you must give a strong justification for not using an 
existing formatting property or properties that are related to the proposed 
new property

[There is a similarity between the above example and some of the examples 
used with TAG Issue 13
    http://www.w3.org/2001/tag/ilist#mixedNamespaceMeaning-13;
both concern mixing of namespaces, but the above example is focused on a 
different aspect of the mixing problem than that addressed by TAG Issue 13.]

Assuming that the principle is accepted, there are some practical things 
that need to happen to implement the principle. I do not claim to know all 
of these, but I believe that the following two things would help facilitate 
an implementation. First, there must be a catalog of formatting properties 
that can be consulted by WG's thinking about formatting property extensions.

Second, it would be useful to have a forum in which WG's could announce 
areas in which they expected to make formatting property extensions so that 
other WG's might see areas where they have interest in common and could 
cooperate with the WG that wants to make an extension.

For some number of years, I have been focused on making it possible for the 
collection of format oriented working groups to share formatting properties.

I have done this at both the top levels of the W3C, to the AC and Team 
management, at the bottom levels, as a member of (or reviewer of) WGs that 
use formatting properties and at a middle level by participating in the 
Hypertext Coordination Group.

At all these levels one of my primary concerns has been the creation of a 
common set of formatting properties that work across the collection of 
document formatting specifications. To this end, I put together (a first 
draft of) a catalog of the formatting properties in use by the W3C RECs. I 
have educated one WG about the work of other WGs in the same area and shown 
how the prior work can be re-used. I have drafted proposals that can work 
across more than a single WG. This has helped to foster a common set of 
formatting properties.

I have retired as a full time employee and contributor to the W3C. I am no 
longer able to perform the function which I had been performing. I strongly 
fear that without architectural affirmation of the principle of a common, 
shared set of formatting properties, that the second law of thermodynamics 
will quickly lead to a non-inter-operable set of formatting properties with 
independent islands of use.

         Steve
=====================================
Steve Zilles
115 Lansberry Court,
Los Gatos, CA 95032-4710
steve@zilles.org
Received on Wednesday, 8 May 2002 23:46:45 GMT

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