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Subject: Re: [cgmo-webcgm] "null" to "empty string"

Tuesday, September 6, 2005, 8:36:43 PM, Lofton wrote:

LH> At 07:42 PM 9/6/2005 -0400, Benoit Bezaire wrote:
>>we agreed that 'nothing to return' for WebCGMString would return
>>an empty string (i.e., "" in JS). See:
>>There were no objections or alternate proposal sent to the mailing

LH> As I mentioned earlier, this resolution was not completely
LH> implemented in the CD2 text.
Yes, and I'm more or less saying that it irrelevant if the spec says
return null or empty string (for WebCGMString). As I explained in the
link above; the ECMAScript binding forces an implementation to return
empty string ("[...] String and null, cannot be compared (see page
55/56) because they are of different types). You are not compliant if
you do other wise.

LH>   Here is the proposed fix (in detail).

LH> Following are the places where the null / empty-string distinction might
LH> apply.  I have indicated any needed changes:

LH> (WebCGMNode.)nodeValue:  in the table above change the 4 occurrences of
LH> "null" to "empty string".
LH> (WebCGMNode.)namespaceURI:  change "null" to "empty string"
LH> (WebCGMNode.)prefix:  change "null" to "empty string"
LH> (WebCGMNode.)localName:  change "null" to "empty string"
LH> (WebCGMNode.)getAttributeNS return value:  okay (already says "empty string")
LH> (WebCGMPicture.)getAppStructureAttr return value:  okay (already says
LH> "empty string")
LH> (WebCGMAttr.)name:  s/is different from null/is different from empty string/
LH> (WebCGMAttr.)value:  says nothing, but refers to getAppStructureAttr (so
LH> does that suffice?)

LH> All okay so far?
Not really. If you start using "empty string" in the specification,
you are tieing the spec to the ECMAScript binding, thus, possibly
preventing other bindings to be developed (i.e., a python binding may
in fact use NULL instead of empty string -just an example-). That's
why I believe the XML DOM often uses NULL/null as a return value
(regardless of the return type).

LH> These are all attributes or method return values of type WebCGMString,
LH> where the question might reasonably arise.  For some others, like 
LH> WebCGMPicture.pictid, nothing is said, but it corresponds to the CGM BegPic
LH> identifier parameter.  I figure if that was "" in the metafile, then it was
LH> unambiguous that the implementation would return "".  Reasonable?  Or
LH> should we say something?

LH> If no objections, I will implement these changes in the text.
I think we need more discussion on this.

LH> -Lofton.

 Benoit   mailto:benoit@itedo.com

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