[x3d-public] [x3d] Spec Comment by brutzman on 19775-1: Abstract X3D Definitions - V3.3

Thu Dec 8 10:06:03 PST 2016

[Specification comment moved to x3d-public list]

Curious topic came up in today's CAD Working Group teleconference regarding the sharing of X3D metadata among multiple scenes, or externally to an individual scene.

One sensible way to do this might simply be as an X3D scene containing just the metadata.  For example:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE X3D PUBLIC "ISO//Web3D//DTD X3D 3.3//EN" "http://www.web3d.org/specifications/x3d-3.3.dtd">
<X3D profile='Immersive' version='3.3' xmlns:xsd='http://www.w3.org/2001/XMLSchema-instance' xsd:noNamespaceSchemaLocation='http://www.web3d.org/specifications/x3d-3.3.xsd'>
   <head>
     <meta content='MetadataRootNodeTest.x3d' name='title'/>
     <meta content='Is a Metadata node legal as the root node in a scene?' name='description'/>
   </head>
   <Scene>
     <MetadataSet name='test'>
       <!-- enter other Metadata nodes here -->
     </MetadataSet>
   </Scene>
</X3D>

Here is a specification comment that will get tracked as a Mantis issue for in-depth consideration and resolution.  All opinions and practice are welcome.

Comment on 19775-1: Abstract X3D Definitions - V3.3
7 Core component
http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/core.html

-----------------
Subject: MetadataSet or Metadata* node(s) as root nodes

Problem statement.  A candidate use case for a collection Metadata* node(s)
is creation of an X3D scene that only includes a collection of such metadata.
This might be desirable for portability or for privacy.

Node typing means that Metadata* nodes are handled differently in X3D XML
Schema and X3D DTD.

Putting Metadata* nodes inside a WorldInfo seems to work well for X3D.
However this does not translate perfectly when converting back to VRML97.

Similarly a single parent Group node might contain the MetadataSet
collection, providing clear context regarding the scope of the MetadataSet
with respect to other nodes in the scene.

Allowing a single MetadataSet as a root child might also address this issue,
but the legality of this approach is unclear.  The value of the field
relationship (e.g. containerField) needs to be considered closely.

Suggested solution: explicit support needs to be declared and demonstrated
for MetadataSet or Metadata* node(s) as a root node in a scene.
Alternatively give guidance on semantics when such global metadata is
provided either within a top-level WorldInfo or ancestor Group node.
-----------------

Submitted on Thursday, 2016,  December 8 - 9:51am
by brutzman (brutzman )

Web3D Standards Comment Form
http://www.web3d.org/content/web3d-standards-comment-form

all the best, Don
-- 
Don Brutzman  Naval Postgraduate School, Code USW/Br       brutzman at nps.edu
Watkins 270,  MOVES Institute, Monterey CA 93943-5000 USA   +1.831.656.2149
X3D graphics, virtual worlds, navy robotics http://faculty.nps.edu/brutzman