[x3d-public] Requirement for v4. Different ids for X3D or scene element

[Leonard Daly]

On 1/31/2019 3:49 PM, John Carlson wrote:
> As a web3d member, how much weight do I personally have to impact the 
> standard?  I would like to see the requirement for different ids in 
> the scene or X3D element in case I load a file into the page in more 
> than one place.


John,

Each file and PROTO define their own namescope. That means you can 
Inline a file many times and not have an ID conflict (in spec-compliant 
X3D). If X3D is brought into a browser with the same functionality 
(using Inline as an example), then the newly added nodes would have the 
same ID. While this is not fatal in an HTML sense, it does lead to an 
ambiguity when using a standard DOM call such as document.getElementById 
(<id-string>).

There is no mechanism in X3D to rename IDs (or DEFs) to avoid that name 
conflict *AND* have all nodes loaded into the DOM. If you create a 
shadow DOM(*) for each external reference (Inline, PROTO (however, that 
is handled), EXTERNPROTO, etc.) then there is no problem because 
elements in shadow DOMs are not available through calls like 
document.getElementById (<id-string>). In those cases it would be 
necessary to provide the appropriate shadow DOM root reference to 
replace 'document'.

The X3D engine would need to intercept all references to those objects 
and make the appropriate change in reference. It's all software, so it 
is doable; but this does break the conceptual model of HTML where all 
visible elements are part of the document.

Note that there is also a similar conceptual breaking for DEF/USE. HTML 
elements only have a single parent. That means something that is USEd 
from someplace else, must be a full copy of the source. It is possible 
to create a 'redirect' element that in the DOM references the DEF 
element so the scene graph (which is typically separate from the DOM 
data structure) is done in the X3D manner.


Leonard Daly




>
> The main requirement for this comes from scripting...how to access the 
> right field if it’s loaded more than once.
>
> Which may be a good reason not to support fields in Scripts or Scripts 
> at all.
>
> John
>
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-- 
*Leonard Daly*
3D Systems & Cloud Consultant
LA ACM SIGGRAPH Past Chair
President, Daly Realism - /Creating the Future/
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