[x3d-public] VRML grammar generator. Was: Re: [...] HAnim2 X3D4 BoxMan update: does ClassicVRML Grammar allows ROUTE in children?

Thu Jan 5 15:45:39 PST 2023

While I tried to find an issue with the VRML grammar, and i had several
misperceptions, and on review, i didn’t find any problems that just “popped
out.”   Perhaps my dry eyes have worsened.

Perhaps we should provide generation of VRML grammar from X3DUOM, if not
done already?  We can have thousands of checks of examples against VRML
grammar, as you have said.   I have not kept track of VRML “stuff.”

Your thoughts?  I know everyone (besides me) is busy.

I can even try to accomplish myself with existing grammar and X3DUOM.   I
can try with writing Xslt first, and if that’s too burdensome, possibly
start from the JSON schema generator and branch out.

Trying to make this as easy for someone to do as possible, can we make the
right implementation choice?   What limitations?  Declarative
implementations seem important.

I agree that supporting one-offs in X3D Validator is useful and we probably
don’t want to support batch web-based validation at this time.

I have also researched “schema from example” and “grammar from example.”
It might be worth applying new AI research to this problem with the right
prompt.

Maybe i should apply AI to the JSON schema.  Hmm!

John

On Thu, Jan 5, 2023 at 11:01 AM Brutzman, Donald (Don) (CIV) <
brutzman at nps.edu> wrote:

> Patrick, thanks for these important insights.
>
>
>
> Am looking closely and tracing the grammar.  As you know, such grammars
> are very important because they formally and unambiguously describe what is
> allowed.  Also pretty tricky to follow!
>
>
>
>    - Extensible 3D (X3D) encodings, Part 2: Classic VRML encoding Annex A
>    (normative), Grammar
>    -
>    https://www.web3d.org/documents/specifications/19776-2/V3.3/Part02/grammar.html
>
>
>
> Am finding following excerpts of interest.  Hopefully addition of
> color-coding helps:
>
>
>
>    1. *node *::=
>
>   nodeTypeId { *nodeBody* } |
>
>   Script { scriptBody } |
>
>   ComposedShader {composedShaderBody} |
>
>   PackagedShader {packagedShaderBody} |
>
>   ShaderProgram {shaderProgramBody} ;
>
>
>    1. *nodeBody *::=
>
>   *nodeBodyElement* |
>
>   *nodeBodyElement* *nodeBody* |
>
>   empty ;
>
>
>
>    1. mfnodeValue ::=
>
>    *nodeStatement *|
>
>    [ ] |
>
>    [ nodeStatements ] ;
>
>
>
>    1. nodeStatements ::=
>
>   *nodeStatement* |
>
>   *nodeStatement* nodeStatements ;
>
>
>
>    1. *nodeStatement*::=
>
>   *node* |
>
>   DEF nodeNameId *node* |
>
>   USE nodeNameId ;
>
>
>
>    1. *nodeBodyElement *::=
>
>   initializeOnlyId fieldValue |
>
>   inputOutputId fieldValue |
>
>   initializeOnlyId IS initializeOnlyId |
>
>   inputOnlyId IS inputOnlyId |
>
>   outputOnlyId IS outputOnlyId |
>
>   inputOutputId IS inputOutputId |
>
>   routeStatement |
>
>   protoStatement ;
>
>
>
>    1. routeStatement ::=
>
>   *ROUTE* nodeNameId . outputOnlyId TO nodeNameId . inputOnlyId ;
>
>
>
>    1. *statement* ::=
>
>   *nodeStatement* |
>
>   importStatement |
>
>   exportStatement |
>
>   protoStatement |
>
>   routeStatement ;
>
>
>
>    1. sfnodeValue ::=
>
>   *nodeStatement *|
>
>   NULL ;
>
>
>
>
>
> So it looks like there are several chains of interest as follows:
>
>
>
>    1. mfnodeValue > nodeStatements > *nodeStatement* > *node *>
>    nodeTypeId {* nodeBody* } > *nodeBodyElement* > routeStatement >
>    *ROUTE*
>
>
>
>    1. sfnodeValue > *nodeStatement > *(etc. as shown immediately above in
>    chain 1)
>
>
>
>    1. *statement* > routeStatement > *ROUTE*
>
>
>
> From these three chains in ClassicVRML grammar, it appears logical to
> conclude that *ROUTE* is allowed to appear wherever an MFNode, SFNode or
> statement is allowed to appear.
>
>
>
> That would be a consistent match with the parent-child relationships
> defined in X3D XML Schema and DTD.
>
>
>
> Hopefully I have the chain of logic correct here.  All scrutiny and review
> is welcome, we definitely need to get this right.
>
>
>
> If there is any unintended omission in the Backus-Naur logic here, then
> great!  We can agree now on corrections, and fix any issues in this year’s
> expected update of the ClassicVRML encoding from X3D3 to X3D4.  Correction
> of converters can also proceed immediately upon achieving consensus.
>
>
>
>    - Wikipedia:  Backus-Naur form
>    - https://en.wikipedia.org/wiki/Backus-Naur_form
>
>
>
> Again thanks for careful strictness, careful checking of model content is
> one of our greatest strengths.
>
>
>
> Have fun with ClassicVRML X3D!  8)
>
>
>
> 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 https://
> faculty.nps.edu/brutzman
>
>
>
> -----Original Message-----
> From: x3d-public <x3d-public-bounces at web3d.org> On Behalf Of Patrick Dähne
> Sent: Thursday, January 5, 2023 3:05 AM
> To: Joseph D Williams <joedwil at earthlink.net>
> Cc: X3D Public Mailing List (x3d-public at web3d.org) <x3d-public at web3d.org>
> Subject: Re: [x3d-public] [...] HAnim2 X3D4 BoxMan update
>
>
>
>
>
> > Am 05.01.2023 um 03:33 schrieb Joseph D Williams <joedwil at earthlink.net
> >:
>
> >
>
> >             • Classic VRML does not allow to declare ROUTEs inside
> MFNode fields. Move them outside.
>
> >
>
> > There may be other x3d Statements and some rules, but I don’t see any
> spec language for what you describe regarding ROUTE.
>
>
>
> The (only) relevant part of the „Classic VRML encoding“ spec is „Annex A:
> Grammar“:
>
>
>
> https://www.web3d.org/documents/specifications/19776-2/V3.3/index.html
>
>
>
> The grammar is written in Backus-Naur form. It is the „Scheme“ of classic
> encoding. Have a look at the rule „mfnodeValue“. You won’t find the symbol
> „routeStatement“ on the right hand side of that rule.
>
>
>
> ROUTEs are only allowed:
>
>
>
> 1. At the top level of the scene
>
> 2. Inside the node body (between fields)
>
>
>
> In my opinion it does not make much sense to forbid ROUTEs inside MFNode
> fields, and I am actually surprised that someone implemented it such
> strictly.
>
>
>
> Bye,
>
>
>
> Patrick
>
>
>
>
>
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>
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>
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