ISSUE: deprecation of old objBehaviors

[Lofton Henderson <lofton@rockynet.com>]

Ref: 
http://lists.oasis-open.org/archives/cgmo-webcgm/200509/msg00093.html
Comments #14, 26
----------

ISSUE sub-1:  Should the 3 deprecated object behaviors remain in the
EBNF of WebCGM 2.0?

ISSUE sub-2:  Should WebCGM 2.0 define a mapping for the 3
deprecated object behaviors?

DISCUSSION:

Dieter wrote, concerning our three old object behaviors, view_context,
highlight, highlight_all, "The 3 deprecated behaviors [should be]
still a part of the EBNF, they may be found in any existing file [...] If
we strike the behaviors from the EBNF, a WebCGM 1.0 file can not be a
valid WebCGM 2.0 file IMHO."  

This is a direct consequence of our definition of
"deprecate":  a deprecated feature is prohibited for 2.0
generators and 2.0 content, but 2.0 interpreters (viewers) that support
1.0 must support the feature.  See A.2.  This
"deprecate" definition was borrowed from MathML, and we have
reviewed it, but perhaps without appreciating its implications.  It
does mean that 1.0 content containing 2.0-deprecated features is not
valid 2.0 content.  

This is an unavoidable consequence of removing anything from a
standard.  One can mitigate the real impact by putting
backward-compatibility requirements on viewers (e.g., like our
"deprecate" definition).

Here is a list of affected things, were deprecated in 1.0 2nd Release and
are (currently) removed altogether in 2.0:

** multi-picture
** continued APS
** symbol libraries

And these things are deprecated in 2.0 and may be removed altogether in
the future:

** viewport PARAM
** some compression types of TILE & BITONAL
** the 3 old object behaviors

It is a tricky issue, how to deprecate and remove something from the
standard.  No matter how you do it, at some point valid Version n
content cannot be valid Version n+1 content.  The only alternative
is to leave everything in the standard forever, as valid
content.

Back to the EBNF ... it defines the version 2.0 language.  If the 3
obj. behaviors are deprecated, according to our definition of deprecated,
they are not part of the 2.0 language.

If anyone has an alternative, coherent, actionable way to define
deprecation and handle things that we think should be removed from the
standard, please present it.  

RECOMMENDATION sub-1:  Leave it as in CD2 -- our definition of
"deprecate", the deprecation of 3 old objBehaviors, and the 2.0
EBNF.

RECOMMENDATION sub-2:  Add Dieter's suggested mapping (cmmt #26) to
3.1.2.4.1, for converting 1.0 content to 2.0 content:
view_context --> zoom+newHighlight
highlight --> newHighlight
highlight_all --> newHighlight

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