XCF and "inherit" value

[Lofton Henderson <lofton@rockynet.com>]

On 11-may, we resolved to add "inherit" value to 'interactivity' and 
'visibility' APS Attributes.  The minutes say something about "...require a 
change to the XCF DTD".

I'm editing now.  Just to be clear, "inherit" will be allowed in the WebCGM 
2.0 metafile instance, in the applicable DOM places, and in the XCF, correct?

Next, while editing the XCF, this interesting question came up.  Is 
"inherit" a valid value for visibility and interactivity on the 'layer' 
element?

Recall that the WebCGM content model requires layer (if present) is the 
top-level object within a picture.  So there is no APS above a 'layer', 
from which to inherit.  (As shown in figure 5.1b, above 'layer' is Picture 
and Metafile, neither of which carry these attributes, AFAIK.) So if the 
value (visibility and/or interactivity) are not specified for a layer, they 
would seem to take the Initial Value, "on".

We could stop there, and make some such ad hoc specification to solve the 
layer question.  But the same question pops up if there are one or more 
top-level (just below Picture) 'grobject' in the picture.  Which leads to 
the real question, about the inheritance model...

When I turned to the inheritance stuff of 5.4 to try to sort it out ... 
more questions than answers.  The inheritance discussion of 5.4.1.1 (et 
al), talks about going up the branch to look for values, if the node is 
"..not the root of the document tree".  Neither layers nor top-level APSs 
can be the "root" of the document tree -- there can be multiple sibling 
layers, and we need a single "root".   So aside from whether or not 
"inherit" is valid for these attributes on layer, what is the "root" for 
the purposes of the inheritance discussion?

It seems to me that the parentNode attribute on a layer or a top-level APS 
would be the Picture, right?  So for the purposes of the inheritance model 
discussion, do we need to say that it is a "virtual APS" that has the 
Initial Value of the ApsAttrs in question?  (And if "yes", then ... well 
the Picture isn't the root yet, is it?  The Picture's parentNode attribute 
is the Metafile, right?  Same question there.)

Thoughts?  How can we deal with this cleanly?

-Lofton.