[tei-council] facsimile diagram

[Conal Tuohy]

Dot wrote:
>> James reminded me that there is work in the MPEG/ISO/W3C communities on
>> defining new Xpointer schemes to point into assorted kinds of multimedia
>> which we should at least acknowledge somewhere.
>>
> Conal had looked into this several months ago and had I believe
> included it in a very early draft of the plan, but at that time the
> multimedia Xpointer scheme was only for pointing into audio/video
> files and not into still images (which would have made our work much
> easier). This may have changed.

I think that's right, and I still believe that using URI fragment identifiers for pointing into images is not an useful approach. 

A particular URI fragment identifier syntax is defined only for a particular set of internet media types.

So HTML has a fragment identifier syntax in which the identifier is a pointer to either an @id attribute, or the @name attribute of an <a> element. XML has a complex syntax in which the identifier refers to an element with a matching @xml:id attribute, or it can use XPointer. SVG has that, too, and also has an "svgview" alternative. 

But these different syntaxes apply only to HTML, XML, and SVG respectively; other media types need to have registered their own fragment identifier syntax, and neither JPEG, TIFF, GIF nor PNG images (I am pretty sure) have such a syntax defined. The MPEG group's pointer syntax applies only to MPEG video (or did, when I looked into it). 

I believe that the facsimile markup should therefore not rely on fragment identifiers, since at best they will be too varied to be helpful, and at worst, they will simply not be defined for many useful image types.