[x3d-public] Finding more than one use of a DEF in VRML

[Don Brutzman]

This is why the vast majority of the models in X3D Examples Archives are carefully scrubbed with regression testing QA tools to avoid ambiguous or erroneous content.

We have only a handful of scenes to test pathologies, these are designed for checking tool diagnostics.

Getting to (a) strict validation wherever possible, and (b) best practices otherwise, provides a path to consistently correct X3D content working everywhere.

Related point: the X3D specifications avoid detailed requirements for failure modes, instead preferring phrasing like "response illegal values is undefined."  This avoids imposition of error-handling requirements for best performance, it also allows browser builders more flexibility in how they handle error conditions.

On 3/25/2020 10:20 PM, John Carlson wrote:
> It would seem like one browser would show the wrong testing result image, and thus would be non-conforming to the conformance test suite.
> 
> John
> 
> On Wed, Mar 25, 2020 at 10:16 PM GPU Group <gpugroup at gmail.com <mailto:gpugroup at gmail.com>> wrote:
> 
>     double defining:
>     - this stymied me too, until I realized the DEF/USE are just for the parser, and its the sequence that counts although different for different browsers.
>     - if you redef 3 times, then USE, what will you get?
>     - that depends on the web3d browser, with some sticking to the first DEF, some the last DEF.

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