[x3d-public] X3D file conformance philosophy

[Andreas Plesch]

Hm,

to me a validation tool is simply not able to reason about or make any
judgement about nodes and fields it does not know anything about (other
than that it does not know them). So to me the main (perhaps only) point of
a validation tool is to pick up out of bound fields, missing DEFs for
routes, missing required nodes, and such. And existing tools do that well,
I think.

So, yes, I think a reduced activity tool would be very useful, and there
may be a way to disable warnings about unknown elements in the validator
bundled with x3d-edit. Could it be done ?

I think the existing phrasing in the spec. for conformance captures well
what valid x3d content is, except for items e), f) and perhaps h) in

http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/conformance.html#ConformanceX3Dfiles

which would not relate to validity if understood in a more inclusive sense.

A concern may be that it would not be possible to flag '<Tansform>' as
syntax error which is clearly desirable. And as a consequence all unknown
elements have to be defined as syntactically incorrect.

But would it not make sense to separate this concern from concerns which
actually can be addressed more specifically by what is contained in the
spec. such as out of bound fields ? Have two buttons, one for possible
syntax errors, and one for deeper, x3d related checking ?

Best regards,

Andreas


On Thu, Sep 24, 2015 at 8:46 AM, Roy Walmsley <roy.walmsley at ntlworld.com>
wrote:

> Andreas,
>
> Referring to your final comment below I would say that a validation tool
> that does not complain about nodes and fields it does not know would make
> that tool largely useless! After all, apart from picking up out of bounds
> field values, or detecting missing required content, the point of a
> validation tool is to complain about things it doesn't recognise. How else
> does it tell you about errors? Validators, if they are well written, will
> already tell you what sort of problem they have found, i.e. the equivalent
> of your classification of deviations.
>
> It sounds like you either need a reduced activity validation tool, or else
> to teach your validation tool about the extra things that you permit in
> your X3D authored files.
>
> Finally I would raise two questions: What is valid X3D content? How does a
> validation tool definitively categorize custom content from errors in valid
> X3D content?
>
> Best regards,
>
> Roy
>
> -----Original Message-----
> From: Andreas Plesch [mailto:andreasplesch at gmail.com]
> Sent: 24 September 2015 13:13
> To: Roy Walmsley
> Cc: X3D Graphics public mailing list
> Subject: Re: [x3d-public] X3D file conformance philosophy
>
> Roy,
>
> you bring up many good points. I completely agree that there are many ways
> to extend the standard.
>
> This includes the option for browsers to provide DTD and Schema for
> extensions which quite a few browsers support. However, in practice this is
> rarely done.
>
> You are right that validation software can only detect deviations from the
> standard as a reference. But I think it could be designed to classify
> deviations into ones which contradict references and ones which it cannot
> further analyse because reference documents do not provide the necessary
> information. In fact, many validators may already do that.
>
> So what could be done ?
>
> In order to be more inclusive, Web3d could introduce a definition of
> validity in parallel to conformance which would allow more documents to
> claim that they have valid x3d content alongside custom content.
>
> I think, in practice all I may be looking for is for a validation tool
> which does not complain about nodes and fields it does not know.
>
> Andreas
>
> On September 24, 2015, at 5:13 AM, Roy Walmsley <roy.walmsley at ntlworld.com>
> wrote:
>
> Andreas,
>
> I would also offer the following consideration into the debate, continuing
> with the current terminology just for the sake of maintaining clarity of
> understanding between us.
>
> Let's say I am a software engineer developing software that validates an
> X3D file,  utilising either or both of the DTD and the Schema. I design my
> software to detect 'deviations' in X3D files from the DTD/Schema reference
> documents. When such 'deviations' are found, how are they to be reported?
> My software isn't going to know if a 'deviation' is an author's intention
> or simply a mistake. It can  only report (notwithstanding very clever
> heuristics) that the X3D file is not valid, pointing out the errors.
>
> Of course, the author also has the option of creating extensions to the
> Schema and or DTD that cover the differences. These would allow software
> validators to pass an X3D file containing extensions above and beyond the
> specifications.
>
> Of course, when we are talking DTD and Schema we are also talking XML.
> Which, of course, stands for  Extensible Markup Language. So an author
> already has the option to make their own private additions.
>
> And then, an author can just create their X3D file with additions, and
> ignore error messages from validation tools.
>
> So, from the perspective of the Web3D Corporation (and here I am only
> expressing my own personal opinion), what can be done? The Corporation does
> not wish to control authors content, merely to provide a standard to enable
> the widespread use and distribution of 3D graphics content. While this
> naturally has limits, it also includes methods to permit individual author
> extensions. HTML is standardized, with validators. It too provides methods
> for extension of the basic standards. Perhaps for HTML these are more well
> known, whereas for X3D they are less publicized.
>
> Best regards,
>
> Roy
>
> -----Original Message-----
> From: Andreas Plesch [mailto:andreasplesch at gmail.com]
> Sent: 24 September 2015 04:51
> To: Roy Walmsley
> Cc: X3D Graphics public mailing list
> Subject: Re: [x3d-public] X3D file conformance philosophy
>
> Roy, thank you for your thoughtful response.
>
> Of course, authors who choose to include non-standard elements are not
> able to have an expectation that the content renders as intended in all
> browsers. In a sense, labeling such content as not conforming is redundant.
> To me, perhaps a better use of the label 'conforming' would be simply an
> assurance that used nodes and fields which are actually standardized
> conform to the standard, eg. <Box size='square' /> would be not conforming.
>
> So I am still not quite sure what the benefit is of considering foreign
> elements in terms of conformity.
>
> From a semantic point of view, perhaps a better fit would be purity or
> fidelity. A pure x3d file consists exclusively of standardized components.
>
> Validity would be another concept which to me signals a tolerance. All x3d
> standardized components in a valid x3d file conform to the standard but it
> may also contain other (xml) content.
>
> Considering that part of the success of html is often seen as due to its
> nonchalance towards unspecified content, this kind of dry discussion is
> probably more relevant than it seems.
>
> Andreas
>
> On Wed, Sep 23, 2015 at 6:51 PM, Roy Walmsley <roy.walmsley at ntlworld.com>
> wrote:
>
> Hi Andreas,
>
>
>
> You have expounded an interesting view.
>
>
>
> What if Conformance did not apply in the restricted sense. An X3D author
> would be able to create files that had additional undefined (and
> non-conforming) content. Browser implementers they would be then be free to
> support whatever extras they wished and still be classed as ‘conforming’.
> So, suppose an author creates an X3D file with extras that is supported on
> one particular browser. If the author were to share the file with others
> they may be restricted to only using the one particular browser that
> supports those particular extras. Other ‘conforming’ browsers would be
> unable to display the content.
>
>
>
> Obviously, it is desirable that X3D authors, should they wish, be free to
> share their X3D files with other users. The concept of restricted
> conformance ensures that if that same file is loaded into other conforming
> browsers then the display will be the same, reproducing the authors
> intentions.
>
>
>
> There are mechanisms already available for authors to generate conforming
> content that has additional features. The first and most obvious is the use
> of Prototypes. The second is to have definitions for additional nodes, both
> in terms of specification and validation tools such as DTD and Schema.
> These can be registered and made publicly available if it is envisaged that
> they will have sufficiently wide usage. Of course, there is ways the
> ultimate third case, whereby additional features are incorporated into the
> specifications. Anyone can present drafts for consideration to the Web3D
> Consortium, provided they have at least two implementations to support the
> new features.
>
>
>
> So my personal view is that it is better to retain the restricted
> conformance testing. But I am always open to further discussion ….
>
>
>
> Best regards,
>
>
>
> Roy
>
>
>
> From: x3d-public [mailto:x3d-public-bounces at web3d.org] On Behalf Of
> Andreas Plesch
> Sent: 23 September 2015 18:55
> To: X3D Graphics public mailing list
> Subject: [x3d-public] X3D file conformance philosophy
>
>
>
> Using the x3d validator and quality assurance tools which come with
> x3d-edit, it will become quickly apparent that an x3d file is deemed
> conforming (or syntactically correct) only after it passes a series of very
> strict tests which are defined here:
>
>
> http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/conformance.html#ConformanceX3Dfiles
>
>
>
> For example, referencing a field of a node which is not listed in the
> spec. but is supported by a x3d browser (say "id") will put the x3d file in
> the unconforming category. Is this correct ?
>
> Similarly, referencing nodes and behaviours which are not explicitly
> defined in the spec. will break conformance.
>
> This is in contrast to the concept of validity of html files which are
> deemed valid even if they include elements not defined in the spec.
>
> So, what is the philosophy of having a narrow definition of file
> conformance ?
>
> It may be that it defines minimum functionality for a x3d browser.
>
>
>
> A x3d browser is said to be conforming when it allows browsing of a
> conforming file as a minimum requirement.
>
> But this convention would still apply if a conforming file could include
> custom (non-spec.) nodes and fields which a conforming browser would be
> allowed to ignore.
>
>
>
> Another way to think about the usefulness of strict conformance may be to
> explore the consequences of restricting tests for conformance only to
> nodes, fields, behaviours and such with which the spec. is actually
> concerned. What would break if ignoring all other elements in browsers and
> parsers would be considered conforming ?
>
> In my view, a strict view of file conformance shifts responsibility from
> the browser to the x3d content author. To me, this is a somewhat inverted
> view which may need to be reconsidered.
>
>
>
> -Andreas
>
>
> --
>
> Andreas Plesch
> 39 Barbara Rd.
> Waltham, MA 02453
>
>
>
>
> --
>
> Andreas Plesch
> 39 Barbara Rd.
> Waltham, MA 02453
>
>
>
>


-- 
Andreas Plesch
39 Barbara Rd.
Waltham, MA 02453
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