[x3d-public] x3d.py roundtrip for Metadata nodes in v.3.3 and v.4.0

Tue Oct 31 11:24:24 PDT 2023

Another idea is to write a post-processor to add containerField output.
I’m not volunteering.

John

On Tue, Oct 31, 2023 at 12:21 PM Andreas Plesch <andreasplesch at gmail.com>
wrote:

> x3d.py may not quite manage a roundtrip back to XML for MetadataSet.
>
>
> https://www.web3d.org/x3d/content/examples/X3dForWebAuthors/Chapter01TechnicalOverview/EmptySceneCoreProfileIndex.html
>
> has the model in XML encoding:
>
> ..
> <Scene>
>   <!-- Core profile can only contain WorldInfo and Metadata nodes. here!!!
> -->
>   <WorldInfo title='EmptySceneCoreProfile.x3d'/>
>   <WorldInfo title='EmptySceneCoreProfile.x3d'>
>     <MetadataSet name='NodeSet' containerField='metadata'>
>       <MetadataBoolean containerField='value' name='BooleanData'
> value='true false'/>
>       <MetadataDouble containerField='value' name='DoubleData' value='1 2
> 3'/>
>       <MetadataFloat containerField='value' name='FloatData' value='4 5
> 6'/>
>       <MetadataInteger containerField='value' name='IntegerData' value='7
> 8 9'/>
>       <MetadataString containerField='value' name='StringData'
> value='"Empty Scene" "Core Profile"'/>
>     </MetadataSet>
>   </WorldInfo>
> </Scene>
> ...
>
> Running
> https://www.web3d.org/x3d/content/examples/X3dForWebAuthors/Chapter01TechnicalOverview/EmptySceneCoreProfile.py
>
> with the latest x3d.py confirms well formedness of the .XML() output.
>
> Uncommenting the diagnostic line to print the XML output gives this XML:
>
> <?xml version="1.0" encoding="UTF-8"?>
> <!DOCTYPE X3D PUBLIC "ISO//Web3D//DTD X3D 3.3//EN"
> "https://www.web3d.org/specifications/x3d-3.3.dtd">
> <X3D profile='Core' version='3.3'
> xmlns:xsd='http://www.w3.org/2001/XMLSchema-instance'
> xsd:noNamespaceSchemaLocation='
> https://www.web3d.org/specifications/x3d-3.3.xsd'>
>   <head>
> ...
>  </head>
>   <Scene>
>     <WorldInfo title='EmptySceneCoreProfile.x3d'/>
>     <WorldInfo title='EmptySceneCoreProfile.x3d'>
>       <MetadataSet name='NodeSet'>
>         <MetadataBoolean name='BooleanData' value='true false'/>
>         <MetadataDouble name='DoubleData' value='1 2 3'/>
>         <MetadataFloat name='FloatData' value='4 5 6'/>
>         <MetadataInteger name='IntegerData' value='7 8 9'/>
>         <MetadataString name='StringData' value='"Empty Scene" "Core
> Profile"'/>
>       </MetadataSet>
>     </WorldInfo>
>   </Scene>
> </X3D>
>
> The Metadata containerField attributes of the original XML encoding
> were omitted. This is ok for most Metadata nodes since the default
> containerField value is 'value'.
>
>
> https://www.web3d.org/specifications/X3dSchemaDocumentation4.0/x3d-4.0_MetadataSet.html#Link561
> defines the default value for the MetadataSet containerField attribute
> also as 'value'. However, in the example the containerField attribute
> value for the MetadataSet node needs to be 'metadata' and not 'value',
> in the x3d.py generated XML.
>
> I believe this may be an example of what John encountered.
>
> One option for x3d.py may be to generate containerField attributes for
> all nodes since x3d.py will know the field name for which a node is
> the value. Perhaps it suffices to do this for all nodes where the
> containerField attribute value would not be 'children'. It may not be
> practical to embed the containerField default values for all nodes in
> the x3d.py source.
>
> I just noticed that x3d.py explicitly generates X3D 3.3 xml output.
> The above only applies to X3D 4.0. However, the same issue persists in
> a flipped way with X3D 3.3 which has 'metadata' as default
> containerField value for Metadata nodes. This means in the x3d.py
> generated output all Metadata nodes except for MetadataSet would need
> an explicit containerField value of 'value'.
>
> -Andreas
> --
> Andreas Plesch
> Waltham, MA 02453
>
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