[x3d-public] VRML grammar generator. Was: Re: [...] HAnim2 X3D4BoxMan update: does ClassicVRML Grammar allows ROUTE in children?
Joseph D Williams
joedwil at earthlink.net
Thu Jan 5 18:54:06 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.”
John, Good, that is Good, that is Very Good.
➢ Your thoughts? I know everyone (besides me) is busy.
I just need a simple thing to change V1 names to v2 names, get some dimensions and complete the Part 1 Annex A LOA4.
Joe
From: John Carlson
Sent: Thursday, January 5, 2023 3:45 PM
To: Brutzman, Donald (Don) (CIV)
Cc: Joseph D Williams; Michalis Kamburelis; Patrick Dähne; X3D Public Mailing List (x3d-public at web3d.org)
Subject: VRML grammar generator. Was: Re: [x3d-public] [...] HAnim2 X3D4BoxMan 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> 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:
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
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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