Re: SGML Open recommendations on HTML 3

lilley (
Tue, 21 Mar 95 12:11:36 EST

Steven J. DeRose writes:

> Posting #1 - March 20 , 1995
> Tables
> ------

> We are recommending omitting the separate "units" attribute and permitting
> units (using compatible unit names in the colspec's colwidth attribute) to
> be suffixed directly to the numbers to which they apply. We would recommend
> accepting the full set of measurements in current use in publishing and
> suggest the following abbreviations: px|pt|pi|mm|cm|in (and * to indicate
> a relative width).
> We have intentionally left out ems; although they are frequently useful,
> it seems likely that people will want to mix point sizes in tables,
> and using EMs as a overall unit of measurement will be often open to
> misinterpretation. We suggest that they should also be removed anywhere
> else where they may be misinterpreted in the HTML 3 DTD.

Counter-suggestion: ems are left in (with a clear comment that they may cause
unpredictable results if your stylesheet messes around with multiple point
sizes in the same table). Ems are left in all places that they occur in the
current DTD and added anywhere else that pixels are mentioned but ems are not.

Reason: partially sighted people using large type will want table column widths
to scale up. Specifying column widths in mm, points etc is surely just
hard-coding browser dependencies into the document. People could be using
and screen size from 10 inch to 25 inch and any resolution from 70 to 120
dots per inch - how can you justify putting column widths in real-world units?
Particularly since you talk about conforming to the ICADD model, I would have
thought that the needs of the partially sighted would be considered in this

Similarly, I thought putting image sizes in ems so they scale properly as
the surrounding text is scaled was a great idea, and hoped the alternative of
using pixel sizes was for backwards compatibility only. Currently, there is
a bad enough mismatch between inline images designed on a VGA screen and
displayed on a workstation (640x480 -> 1280x1024 or 1536x1280) and vice
versa. The suggestion of using mm, inch etc for image sizes copes with this
problem but then snookers the partially sighted who need to scale everything
up - way up, like 20 or 30 characters on a 19" screen, using auto scrolling
software to read the long lines - and are left with widdy little images
scattered through their large text.

One way around this (which would work for either separate units or the
SGML Open suggested integrated units)would be for browsers to offer a
magnification feature - 2x, 4x, 8x, 16x - and all units (except ems ;-)) would
scale by this as would all text sizes. In that case it should be stated in the
spec that sizes are rendering hints only and may be ignored or over-ridden
by particular browsers.


Chris Lilley
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