W3C home > Mailing lists > Public > www-svg@w3.org > December 2011

Re: Ignoring trailing semi-colon delimiters

From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
Date: Thu, 1 Dec 2011 12:38:04 +0100
To: www-svg@w3.org
Message-Id: <201112011238.04403.Dr.O.Hoffmann@gmx.de>
Brian Birtles

>[1] Notably, Batik does not allow trailing semicolons for the begin 
>attribute. WebKit and Opera don't support the proposed ";;" syntax for a 
>final empty value.

Well, for begin, according to SMIL, an empty value has to be
treated as event value. Because there is no event '' defined
in SVG or SMIL, such a value will never start an animation.
I think, the SVG recommendations note only, which events are
available or supported, but there is no indication that
it is not allowed to note other  events like '' or 'BigRip'.

Following this, it is useless to note empty begin list items 
or 'BigRip', but not necessarily wrong. Following this you can write
as well begin=";;  ;;5s;; ;BigRip+3s;Big.Bang-10s;; ;  " without any problem.
I checked some variants of this with Opera, but indeed the animation 
does not start after 5s, this looks like a bug.

For most other attributes like keyTimes or keySplines
it is clearly defined, that 
'If there are any errors in the keyTimes specification (bad values, too many 
or too few values), the animation will have no effect.'
or
'If there are any errors in the keySplines specification (bad values, too many 
or too few values), the animation will have no effect.'
or
'If any values (i.e., the argument-values for from, to, by or values 
attributes) are not legal, the animation will have no effect.'

For such cases neither the notation bug of the author has to be ignored,
nor just the attribute with the wrong values.

Therefore the correct behaviour for a trailing semicolon
or other stupid structures like ";;" is to see no effect for most attributes, 
what is a pretty good indication for the author to fix the bug
before publication ;o)
If viewers tend to ignore silently errors, soon the format
gets obfuscated - we can see the consequences easily
for HTML - most published content is stupid tag soup
and there is a huge working draft trying already for many 
years now to explain how to present any stupid tag soup 
in some way, that neither helps authors nor readers 
of such stupid content - and the draft got far to complex
for normal authors already now.

Olaf
Received on Thursday, 1 December 2011 11:38:49 GMT

This archive was generated by hypermail 2.3.1 : Friday, 8 March 2013 15:54:50 GMT