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

Thu Jan 5 16:54:58 PST 2023

Simple summary of ROUTE conversions:

a.	We will allow ROUTEs as children, as always intended.  
b.	If the ClassicVRML Grammar indeed needs modification, we will define
that for Mantis and 2023 ClassicVRML revision.
c.	As soon as we reach consensus, we will ask converters to fix support
for ROUTEs.

Quality assurance (QA) efforts are all focused on XML and X3DUOM mappings to
different program languages. No need to autogenerate a ClassicVRML Grammar
that exists and has pretty-much worked for the past quarter century (since
1997).  If we figure out and confirm an improvement, then wow + bravo
everyone!!  If we determine that it is OK, we’ve learned more too.

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

From: John Carlson <yottzumm at gmail.com> 
Sent: Thursday, January 5, 2023 3:46 PM
To: Brutzman, Donald (Don) (CIV) <brutzman at nps.edu>
Cc: Joseph D Williams <joedwil at earthlink.net>; Michalis Kamburelis
<michalis.kambi at gmail.com>; Patrick Dähne <pdaehne at gmail.com>; X3D Public
Mailing List (x3d-public at web3d.org) <x3d-public at web3d.org>
Subject: VRML grammar generator. Was: Re: [x3d-public] [...] HAnim2 X3D4
BoxMan update: does ClassicVRML Grammar allows ROUTE in children?

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 <mailto: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.h
tml

Am finding following excerpts of interest.  Hopefully addition of
color-coding helps:

a.	node ::=

  nodeTypeId { nodeBody } |

  Script { scriptBody } |

  ComposedShader {composedShaderBody} |

  PackagedShader {packagedShaderBody} |

  ShaderProgram {shaderProgramBody} ;

b.	nodeBody ::=

  nodeBodyElement |

  nodeBodyElement nodeBody |

  empty ;

c.	mfnodeValue ::=

   nodeStatement |

   [ ] |

   [ nodeStatements ] ;

d.	nodeStatements ::=

  nodeStatement |

  nodeStatement nodeStatements ;

e.	nodeStatement::=

  node |

  DEF nodeNameId node |

  USE nodeNameId ;

f.	nodeBodyElement ::=

  initializeOnlyId fieldValue |

  inputOutputId fieldValue |

  initializeOnlyId IS initializeOnlyId |

  inputOnlyId IS inputOnlyId |

  outputOnlyId IS outputOnlyId |

  inputOutputId IS inputOutputId |

  routeStatement |

  protoStatement ;

g.	routeStatement ::=

  ROUTE nodeNameId . outputOnlyId TO nodeNameId . inputOnlyId ;

h.	statement ::=

  nodeStatement |

  importStatement |

  exportStatement |

  protoStatement |

  routeStatement ;

i.	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

2.	sfnodeValue > nodeStatement > (etc. as shown immediately above in
chain 1)

3.	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
<https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fen.wikipe
dia.org%2Fwiki%2FBackus-Naur_form&data=05%7C01%7Cbrutzman%40nps.edu%7Cb358dc
688cae4c8421b408daef76faef%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C6380
85591553880829%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiL
CJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=KzgMBB%2F7DwoJbxm3aoofTI
U%2F0Be6BiZ1r9Mnj8w%2F6Q4%3D&reserved=0> 

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
<mailto: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 <http://faculty.nps.edu/brutzman> 

-----Original Message-----
From: x3d-public <x3d-public-bounces at web3d.org
<mailto: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 <mailto:joedwil at earthlink.net>
>
Cc: X3D Public Mailing List (x3d-public at web3d.org
<mailto:x3d-public at web3d.org> ) <x3d-public at web3d.org
<mailto:x3d-public at web3d.org> >
Subject: Re: [x3d-public] [...] HAnim2 X3D4 BoxMan update

> Am 05.01.2023 um 03:33 schrieb Joseph D Williams <
<mailto:joedwil at earthlink.net> 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>
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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