[x3d-public] X3D minutes 5, and 12 March 2012: outreach activity, HAnim, metadata explorations, X3D Ontology, glTF examples

[Michalis Kamburelis]

Don,

As I understand, the proposed change here would say "if there are no
double-quotes (expressed in any way) at the beginning and end of
MFString attribute content, then parse it as a SFString (since
otherwise it would be just invalid MFString)".

1. First of all, this is mostly independent to my proposals on
https://github.com/michaliskambi/x3d-tests/wiki/Clarify-the-usage-of-quotes-and-backslashes-for-MFString-and-SFString-in-XML-encoding
. My point is to clarify the current X3D XML text about how to parse
SFString and MFString (
https://www.web3d.org/documents/specifications/19776-1/V3.3/Part01/EncodingOfFields.html#SFString
)). Clarify it, and also document actual behavior that X3D browsers
already do in practice.

    We've had a number of discussions on x3d-public where it was
apparent that even people closely working with X3D are sometimes
surprised by how SFString and MFString parsing works in X3D XML
:),e.g. how backslashes work. I believe it is because the current X3D
XML spec is a little *too* terse. It doesn't discuss, or show
examples, of some difficult situations.

    So, whatever we do -- we don't really disagree in our main goals
:) My main goal is to clarify the X3D XML spec. I do not really want
to make any changes to what existing browsers actually do.

2. As for the rule you propose (that one can omit double-quotes around
MFString content, when MFString has only one item):

I recall we talked about this. I still do not think above rule is a
good idea (although it's a "soft disagree", not "strong disagree"). My
reasons:

- This is an "exception to the rule", which in general is a sign to
not do something.

- It complicates and already-complicated rules of X3D XML spec about MFString.

- Treatment of backslashes will suddenly change, depending on whether
you used double-quotes or not, because treatment of backslashes
differs between SFString and MFString (and it has to, as we discussed
and I documented on
https://github.com/michaliskambi/x3d-tests/wiki/Clarify-the-usage-of-quotes-and-backslashes-for-MFString-and-SFString-in-XML-encoding
).

I do not think comparing it with classic VRML syntax is valid. In the
classic VRML syntax, the rules are more consistent for SFString and
MFString parsing. For better or worse, SFString and MFString parsing
is already more different in X3D XML syntax, it has to be.

That being said, it's not a "strong disagreement". If such rule would
be clearly explained in the spec (in particular explaining what it
means for backslashes) I can "live wit it" :)


Regards,
Michalis

śr., 17 mar 2021 o 21:41 Don Brutzman <brutzman at nps.edu> napisał(a):
>
> Thanks Michalis.  Agreed this is important to sort out.
>
> Difference of opinion:  I think we can safely relax the prohibition as follows
>
>         The construct "string3" *is* a valid single-array-value instance of an MFString. Such an MFString can also be properly specified as
>         '"string3"'
>         or
>         '"string3"'
>         or
>         ""string3""
>
> This use of a singleton value is already the case for grammar in ClassicVRML encoding.
>
>         The construct "string3" is equivalent to [ "string3" ] or simply "string3" in ClassicVRML encoding.
>
> Clarifications for backslash can always help, I don't have an opinion yet on what you've said.  We do have writeups in Mantis and perhaps-several example test scenes.
>
> Will continue preparations and put this on weekly agenda in near future, though likely not this week.
>
> On 3/16/2021 1:16 AM, Michalis Kamburelis wrote:
> >
> > The issue of quoting MFString and SFString in X3D XML encoding was
> > discussed many times on this mailing list :) I have a page with
> > conclusions on https://github.com/michaliskambi/x3d-tests/wiki/Clarify-the-usage-of-quotes-and-backslashes-for-MFString-and-SFString-in-XML-encoding
> > . Let us apply the fix to the spec, I have a ready prose on that page
> > that I believe was "agreed" by various parties a few years ago already
> > :)
> >
> > Regards,
> > Michalis
> >
> > wt., 16 mar 2021 o 07:21 Don Brutzman <brutzman at nps.edu> napisał(a):
> >>
> >> Attendees  5 March 2021:  Vince Marchetti, Dick Puk, Don Brutzman
> >>
> >> Attendees 12 March 2021:  Anita Havele, Vince Marchetti, Dick Puk, Don Brutzman
> >>
> >> We continue to meet Fridays at regular time, 09-1000 pacific.
> >> [...]
> 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