Appendix E.2 and E.4

Hello all,
 
Lofton and I have spoken and feel that the following meets the action
item to reword sections E.2 and E.4  If there are no objections we will
forward the changes Monday to support the WAI face to face meeting.
 
Thank you for your time.
 
Stuart Galt.
 
 


--
Stuart Galt
SGML Resource Group
stuart.a.galt@boeing.com
(206) 544-3656



E.2 Navigation


By Guideline 9 "Provide navigation mechanisms" of [UAAG10
<http://www.w3.org/TR/2002/REC-UAAG10-20021217/> ] a WebCGM viewer is
expected to let users interact with 'enabled' and significant objects in
the image.  'Enabled' objects are those which accept user input, such as
on screen buttons.  By the structure of WebCGM, each APS should be
treated as a significant object and be reachable by navigation
techniques.  By Guideline 1 "Support input and output device
independence" the reach of keyboard-actuated navigation should cover
this whole set of navigation destinations.

Some notion of forward and backward motion among peer nodes in the
WebCGM image should be provided.  This should by default move among
paragraphs and sub-paragraphs in the order in which they appear in the
metafile.  The creators of WebCGM instances should ensure that this
results in a sensible reading order.  However, efficient motion as
called for in [UAAG10] Checkpoint 9.9
<http://www.w3.org/TR/WAI-USERAGENT/guidelines.html#tech-nav-structure>
, is not likely to result from one global list or loop of all the
plausible navigation destinations.  Exploiting the structure of the
metafile, structured navigation could take hierarchical or categorical
forms.  In hierarchical navigation, forward and back motion moves among
peer nodes at the same level in the layers-and-objects nesting tree.  In
categorical navigation, the sequential navigation could exhibit
navigation modes which visit only 'grobject' nodes, or only the
'gropbject' nodes with a common 'name.'  An example of hierarchical
navigation is provided by the player behavior for the [DAISY] standard
digital talking book.  An example of categorical structured navigation
is provided by the diverse navigation modes of the Opera browser.  The
creators of WebCGM instances should ensure that the layers-and-objects
nesting forms a plausible table of contents as annotated with the
textual properties (see E.3 below) of the affected nodes, and that
collecting nodes of like 'name' forms meaningful slices of what is in
the scene.

In this version of WebCGM, there are no intra-metafile controls to alter
the navigation graph. In a scenario where such capability is desired,
the private-namespace extension feature
<http://www.w3.org/TR/webcgm20/WebCGM20-XCF.html#extending>  of the XCF
can be used to introduce further intelligence associated with the
contents of the metafile proper. 

 ...

 


E.4 Visibility and Navigation


By default, WebCGM viewers allow the user to navigate to and interact
with only enabled elements (i.e. element whose 'visibility
<http://www.w3.org/TR/webcgm20/WebCGM20-IC.html#webcgm_visibility> '
attribute is 'on'). Objects which are not visible do not display
tooltips (the 'screentip' APS attribute), may not be highlighted without
making them visible, and may not be navigated to via the picture
behaviors (whether in picture fragments or DOM src parameter). 

In addition, WebCGM viewers can offer a mode where, at user option, the
'visibility
<http://www.w3.org/TR/webcgm20/WebCGM20-IC.html#webcgm_visibility> '
attribute is ignored, for accessibility or debugging support. It meets a
requirement of [UAAG10] <http://www.w3.org/TR/UAAG10/guidelines.html>
CheckPoint 9.3.