[x3d-public] MFString quotes

[Roy Walmsley]

Hi,

For reference the specification comment raised by Yves has the corresponding
Mantis issue number 1091. For Web3D members this is available at
http://www.web3d.org/member-only/mantis/view.php?id=1091. There were some
follow-up comments by Leonard, Yves, and Don, all dated to 7th/8th December
2016. These are all recorded as notes in the issue. These comments were
distributed on the Web3D members-only list. However, if all three can get
back to me indicating their permission to make these public I will republish
the whole to the public list.

All the best,

Roy

-----Original Message-----
From: x3d-public [mailto:x3d-public-bounces at web3d.org] On Behalf Of Yves
Piguet
Sent: 15 March 2017 08:02
To: Andreas Plesch <andreasplesch at gmail.com>
Cc: X3D Graphics public mailing list <x3d-public at web3d.org>
Subject: Re: [x3d-public] MFString quotes

See also my spec comment 1108 at
http://www.web3d.org/node/1694/submission/1108 for those authorized to read
it (I'm not). I quote it below. To summarize, I think X3D-XML must be
compliant with XML, and 19776-1 shouldn't interfere with what belongs to the
XML standard: define what's stored in the attributes (with double quotes for
MFString), not how (which quotes around the attribute or which encoding for
what must be escaped, be it with entities or not).

Yves

> Comment on 19776-1: XML Encoding - V3.3
> 5.15 SFString and MFString
> http://www.web3d.org/documents/specifications/19776-1/V3.3/Part01/Enco
> dingOfFields.html#SFString
> 
> -----------------
> Confusion between xml and x3d syntax for SFString Problem statement: 
> 5.15 states which kind of quotes should be used for the xml attribute 
> value for SFString and MFString. But that's specified in the xml 
> standard: both single quotes and double quotes are valid. When an 
> XML-encoded X3D file is parsed by a generic XML parser, there is no 
> way to know which kind of quote was used, and that shouldn't be 
> necessary. For an SFString, str="foo" or str='foo' should both be 
> valid; and for an MFString, str='"foo" "bar"' or str=""foo" "bar"".
> Suggested solution: replace
> SFString specifies a single string encoded as a sequence of UTF-8 
> octets enclosed in double quotes (e.g., "string").  The MFString 
> specifies zero or more SFStrings enclosed in single quotes (e.g., 
> '"string1" "string2"') with SFString specifies a single string encoded 
> as a sequence of UTF-8 octets without additional quotes (as an XML 
> attribute value, it must be enclosed in single or double quotes, e.g. 
> "string" or 'string').  The MFString specifies zero or more SFStrings, 
> each of them enclosed in double quotes, separated by at least one 
> space (as an XML attribute value, it must be enclosed in single or 
> double quotes, and conflicting single and double quotes in the content 
> must be written as entities; e.g., '"string1" "string2"'; for more 
> complicated cases with single quotes in the first string and double 
> quotes in the second string, '"\"string1\"" "'string2'"' or ""\"string1\""
> "'string2'"')
> -----------------
> 
> Submitted on Wednesday, 2016,  December 7 - 4:03pm by  (Yves Piguet )
> IP: ***
> 
> See: http://www.web3d.org/node/1694/submission/1108


> On 14 Mar 2017, at 22:55, Andreas Plesch <andreasplesch at gmail.com> wrote:
> 
>
http://www.web3d.org/documents/specifications/19776-1/V3.3/Part01/EncodingOf
Fields.html#SFString
> clearly states:
> The MFString specifies zero or more SFStrings enclosed in single quotes
(e.g., '"string1" "string2"').
> 
> However, at least in Python there seems to be a notion that double quotes
within attribute values in XML should be escaped as " . Also there is a
preference that the outer quotes should be double quotes. This is probably
due to Python XML standard libraries such as elementtree or minidom being
hardcoded to serialize this way.
> 
> This makes it hard to conform exactly to the X3D XML encoding standard. I
am not sure why X3D imposes this use of quotes.  XML allows for both single
and double quotes as outer quotes, and the quotes used in the value could
still be specified as double quotes. They just need to be escaped as entity
if double quotes are used as outer quotes.
> 
>  x3d browsers may behave like this anyways if they use a reasonable XML
parser.
> 
> So I would like to raise if it would be possible to relax the XML encoding
a bit to allow use of standard XML serializer ?
> 
> Andreas
> 
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